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Biomedical subjects

M R Starling

Publications and source records attributed to M R Starling.

At least 37 records · Page 2Linked to original sources
PubMed1993

Impaired left ventricular contractile function in patients with long-term mitral regurgitation and normal ejection fraction.

OBJECTIVES: We tested the hypotheses that left ventricular chamber elastance would detect impaired contractile function in patients with long-term mitral regurgitation and a normal ejection fraction and that these patients would have unique temporal left ventricular size and ejection fraction responses to mitral valve surgery. BACKGROUND: Although it has been suggested that left ventricular contractile function may begin deteriorating in patients with long-term mitral regurgitation whereas ejection fraction remains normal, no data exist in humans. METHODS: We studied 11 control patients and 28 patients with long-term mitral regurgitation using micromanometer-measured pressures, biplane contrast cineventriculography and radionuclide angiography under control conditions and with alterations in load during right atrial pacing to calculate left ventricular chamber elastance and myocardial stiffness. RESULTS: The patients with mitral regurgitation were classified into subgroups: Group I, normal contractile function; Group II, impaired contractile function (reduced Emax) but normal ejection fraction, and Group III, impaired contractile function (reduced Emax) with reduced systolic myocardial stiffness. Twenty-two of the patients with mitral regurgitation underwent mitral valve surgery. In Group I, comparable decreases in left ventricular volume indexes (p < 0.01 and p = 0.05, respectively) were associated with no change in ejection fraction at 3 months and 1 year. In contrast, in Group II, reductions in volume indexes (p < 0.0001 and p < 0.001) were associated with a short-term decrease in ejection fraction (p < 0.001) that recovered at 1 year (p < 0.01 vs. short-term). Finally, in Group III, variable responses in volume indexes were associated with a consistent decrease in ejection fraction at 3 months and 1 year. CONCLUSIONS: An analysis of left ventricular chamber elastance provides data to support the concepts that 1) contractile function is impaired in some patients with long-term mitral regurgitation and a normal ejection fraction, 2) impaired contractile function may not be irreversible in all of these patients, and 3) an earlier consideration of mitral valve surgery may be warranted to preserve contractile function in these patients.

Adult↗
PubMed1993

Effects of alterations in systolic pressure on radionuclide measurements of left ventricular filling dynamics.

To determine the effects of steady-state left ventricular systolic pressure alterations on radionuclide measures of left ventricular filling dynamics, we studied 15 normal patients and 17 patients with nonischemic heart disease. Micromanometer left ventricular pressures and computer assisted forward gated radionuclide angiograms were acquired simultaneously. Right atrial pacing maintained heart rates constant during the baseline condition and methoxamine and nitroprusside infusions. Diastolic filling dynamics, peak filling rate and time to peak filling rate were calculated using a three harmonic Fourier analysis of the left ventricular time-activity curves. Left ventricular systolic pressure increased to 165 +/- 25 mmHg with methoxamine (p < 0.001) and decreased to 106 +/- 18 mmHg with nitroprusside (p < 0.001) from a baseline value of 133 +/- 16 mmHg. Radionuclide left ventricular filling dynamics did not change significantly. Thus, we conclude that radionuclide measurements of left ventricular filling dynamics are not affected by modest, steady-state alterations in left ventricular systolic pressure and can therefore be useful for the assessment of left ventricular diastolic function during interventions which may also affect left ventricular systolic pressure.

Adult↗
PubMed1992

Mechanisms for an abnormal radionuclide left ventricular ejection fraction response to exercise in patients with chronic, severe aortic regurgitation.

To clarify the mechanisms for an abnormal radionuclide left ventricular (LV) ejection fraction response to exercise in patients with chronic, severe aortic regurgitation (AR), we studied seven control patients and 21 patients with AR. We used exercise radionuclide angiography and catheterization of the right and left sides of the heart to obtain a calculation of LV chamber elastance. The control and AR groups had similar heart rates, systolic blood pressure responses to exercise, and exercise durations. In both patient groups, LV end-diastolic volume did not change with exercise. In contrast to the decrease in LV end-systolic volume (p less than 0.05) and increase in LV ejection fraction (p less than 0.01) in the control group, LV end-systolic volume in the patients with AR increased, resulting in little change in their LV ejection fraction. By stepwise multiple regression analysis, the radionuclide LV ejection fraction at peak exercise in patients with AR was determined by the LV chamber elastance, LV end-systolic volume, and stroke volume at peak exercise (cumulative r = 0.79, p less than 0.02); the change in radionuclide LV ejection fraction from rest to peak exercise was determined by the corresponding change in systemic vascular resistance, regurgitant index, and LV end-diastolic and end-systolic volumes (cumulative r = 0.88, p less than 0.02). These data demonstrate that in patients with AR, the radionuclide LV ejection fraction at peak exercise is principally determined by the cumulative effects of chronic, severe AR on LV systolic chamber performance, and the change in radionuclide LV ejection fraction from rest to peak exercise is principally established by peripheral vascular responses.

Aortic Valve Insufficiency↗
PubMed1991

Assessment of right ventricular oxidative metabolism by positron emission tomography with C-11 acetate in aortic valve disease.

Evaluation of right ventricular (RV) oxidative metabolism is limited by the inability to easily determine oxygen extraction by the RV myocardium and the complex morphology of this ventricle. Because left ventricular C-11 clearance rate constants closely correlate with myocardial oxygen consumption, it was postulated that C-11 clearance rate constants for the RV free wall should also reflect its oxygen consumption. Therefore, RV C-11 clearance rate constants were compared with RV loading in 21 patients with aortic valve disease to assess the possible use of this technique for noninvasive evaluation of RV oxidative metabolism. RV free wall C-11 clearance rate constants correlated with the product of systolic pulmonary artery pressure and heart rate for all patients (r = 0.65, p = 0.002), but the relation was stronger if 2 patients with overt RV dysfunction were excluded (r = 0.83, p = 0.001). On the basis of mean pulmonary artery pressures, patients were stratified into subgroups with normal (group I, n = 8) and elevated (group II, n = 13) pulmonary pressures and were compared with 10 normal control subjects. RV C-11 clearance rate constants were significantly higher in group II than in group I and in normal control subjects (p less than 0.05). These data suggest that RV C-11 acetate clearance rate constants can provide noninvasive evaluation of RV oxidative metabolism. This technique may allow serial assessment of RV performance in various cardiac and pulmonary diseases, and particularly of changes associated with therapeutic interventions.

Acetates↗
PubMed1991

Mechanisms for left ventricular systolic dysfunction in aortic regurgitation: importance for predicting the functional response to aortic valve replacement.

To test the hypothesis that the combined use of the time-varying elastance concept and conventional circumferential stress-shortening relations would elucidate differential mechanisms for left ventricular systolic dysfunction in severe, chronic aortic regurgitation and therefore predict the functional responses to aortic valve replacement, 31 control patients and 37 patients with aortic regurgitation were studied. The studies included micromanometer left ventricular pressure determinations, biplane contrast cineangiograms under control conditions and radionuclide angiograms under control conditions and during methoxamine or nitroprusside infusions with right atrial pacing. The patients with aortic regurgitation were classified into three groups: Group I had normal Emax and stress-shortening relations, Group II had abnormal Emax but normal stress-shortening relations and Group III had abnormal Emax and stress-shortening relations. The left ventricular end-diastolic and end-systolic volumes showed a progressive increase and the ejection fraction showed a progressive decrease from Group I to III; these values differed from those in the control patients (p less than 0.001). In Group I, there was a decrease in left ventricular volumes (p less than 0.05) but no significant change in ejection fraction (61 +/- 7% versus 63 +/- 4%) after aortic valve replacement. In contrast, in Group II, reduction in left ventricular volumes (p less than 0.01) was associated with an increase in ejection fraction from 50 +/- 8% to 64 +/- 11% (p less than 0.01). Finally, in Group III, reduction in left ventricular volumes (p less than 0.05) was associated with a further decrement in ejection fraction from 35 +/- 13% to 30 +/- 13%. Group I patients had compensated adequately for chronic volume overload. However, Group II had left ventricular dysfunction that was associated with an increase in the left ventricular volume/mass ratio compared with that in the control patients and Group I (p less than 0.05 for both), suggesting inadequate hypertrophy and assumption of spherical geometry. Finally, irreversible myocardial dysfunction had supervened in Group III. In conclusion, a combined analysis of left ventricular chamber performance using the time-varying elastance concept and myocardial performance using conventional circumferential stress-shortening relations provides complementary information that elucidates differential mechanisms for left ventricular systolic dysfunction and therefore predicts the functional response to aortic valve replacement.

Aortic Valve↗
PubMed1991

Relation between maximum time-varying elastance pressure-volume areas and myocardial oxygen consumption in dogs.

To establish whether pressure-volume areas (PVAs) calculated using the maximum time-varying elastance (Emax) have a relation with myocardial oxygen consumption (MVO2) that improves on other indexes of myocardial oxygen demand, we studied nine dogs of either sex weighing 19-39 kg, which were instrumented with a micromanometer left ventricular (LV) catheter and a Wilton-Webster coronary sinus flow catheter and had red blood cells tagged with technetium-99m for radionuclide angiography. Hemodynamics, coronary sinus flow determinations, and radionuclide angiograms were obtained under control conditions and during three to five steady-state loading conditions (mean +/- SD, 5.6 +/- 0.7). Isochronal pressure-volume data points from each pressure-volume loop were subjected to linear regression analysis to calculate Emax. The Emax relations, diastolic curves, and systolic portions of each pressure-volume loop were used to obtain calibrated PVAs. The Emax PVA (mm Hg.ml.beat-1.100 g-1) and MVO2 (ml O2.beat-1.100 g-1) values correlated in each animal (r = 0.77 to 0.99). Their slopes averaged (3.48 +/- 1.68) x 10(-5) ml O2.mm Hg-1.ml-1, and their y-axis intercepts averaged 0.07 +/- 0.04 ml O2.beat-1.100 g-1. When the MVO2 relations were compared with Emax PVA, LV systolic pressure-rate product, LV stroke work, and a modification of the LV pressure-work index, the Emax PVA, LV systolic pressure-rate product, and LV pressure-work index had similar relations with MVO2, whereas LV stroke work was a weaker index of MVO2 (p less than 0.05 versus Emax PVA). This occurred because the Emax PVA:MVO2 slopes and y-axis intercepts differed in each dog, which was due to differences in basal LV contractility. The Emax PVA:MVO2 slopes correlated with Emax (r = 0.73, p less than 0.05), and the y-axis intercepts were also weakly related to Emax (r = 0.48, p = 0.19). We conclude that the Emax PVAs calculated using data acquisition techniques that are clinically applicable have relations with MVO2 that in general do not improve on other indexes of myocardial oxygen demand in this animal preparation.

Animals↗
PubMed1990

Dissociation of end systole from end ejection in patients with long-term mitral regurgitation.

To determine whether left ventricular (LV) end systole and end ejection uncouple in patients with long-term mitral regurgitation, 59 patients (22 control patients with atypical chest pain, 21 patients with aortic regurgitation, and 16 patients with mitral regurgitation) were studied with micromanometer LV catheters and radionuclide angiograms. End systole was defined as the time of occurrence (Tmax) of the maximum time-varying elastance (Emax), and end ejection was defined as the time of occurrence of minimum ventricular volume (minV) and zero systolic flow as approximated by the aortic dicrotic notch (Aodi). The temporal relation between end systole and end ejection in the control patients was Tmax (331 +/- 42 [SD] msec), minV (336 +/- 36 msec), and then, zero systolic flow (355 +/- 23 msec). This temporal relation was maintained in the patients with aortic regurgitation. In contrast, in the patients with mitral regurgitation, the temporal relation was Tmax (266 +/- 49 msec), zero systolic flow (310 +/- 37 msec, p less than 0.01 vs. Tmax), and then, minV (355 +/- 37 msec, p less than 0.001 vs. Tmax and p less than 0.01 vs. Aodi). Additionally, the average Tmax occurred earlier in the patients with mitral regurgitation than in the control patients and patients with aortic regurgitation (p less than 0.01, for both), whereas the average time to minimum ventricular volume was similar in all three patient groups. Moreover, the average time to zero systolic flow also occurred earlier in the patients with mitral regurgitation than in the control patients (p less than 0.01) and patients with aortic regurgitation (p less than 0.05). Because of the dissociation of end systole from minimum ventricular volume in the patients with mitral regurgitation, the end-ejection pressure-volume relations calculated at minimum ventricular volume did not correlate (r = -0.09), whereas those calculated at zero systolic flow did correlate (r = 0.88) with the Emax slope values. We conclude that end ejection, defined as minimum ventricular volume, dissociates from end systole in patients with mitral regurgitation because of the shortened time to LV end systole in association with preservation of the time to LV end ejection due to the low impedance to ejection presented by the left atrium. Therefore, pressure-volume relations calculated at minimum ventricular volume might not be useful for assessing LV chamber performance in some patients with mitral regurgitation.

Chronic Disease↗
PubMed1990

Is standardization of left ventricular chamber elastance necessary?

Because of the relation between left ventricular (LV) chamber elastance and heart size, it has been hypothesized that maximum time-varying elastance (Emax) must be standardized to differentiate between preserved and depressed LV systolic performance. To test this hypothesis, we studied 66 patients, of whom 25 had a normal LV, 20 had aortic regurgitation, 14 had mitral regurgitation, and seven had cardiomyopathy, with micromanometer-determined LV pressures and radionuclide angiograms during multiple LV loading conditions. Multiple regression analysis established that Emax was independently related to LV end-diastolic volume (r = -0.69). When the Emax and LV end-diastolic volume (EDV) data from all patients were plotted, a curvilinear relation was evident. Data transformation to the base e identified two distinct linear relations, one in the normal patients of lnEmax = -0.60 (lnEDV) +4.34 (r = -0.67, p less than 0.001); and one in the patients with cardiac pathology of lnEmax = -1.06 (lnEDV) +6.12 (r = -0.73, p less than 0.001), which differed from each other (p less than 0.01). When a mathematical standardization was applied to these data to eliminate the independent contribution of heart size to the reduction in lnEmax, the normal patients had a standardized lnEmax versus lnEDV slope of 0, whereas that in the patients with cardiac pathology remained negative and continued to differ from that in the normal patients (p less than 0.001). Dichotomization of patients with cardiac pathology into those with preserved and depressed LV chamber elastance by lnEmax or standardized lnEmax provided highly concordant data (k = 0.73, p less than 0.001). Moreover, the estimated contribution of LVEDV to the reduction in Emax in patients with cardiac pathology averaged only 14 +/- 7%. We conclude from these data that LV chamber elastance calculated with radionuclide angiography has an independent relation with LVEDV, that a mathematical standardization of Emax for heart size does not significantly alter the dichotomization of patients with cardiac pathology into those with preserved and depressed LV systolic performance, and that heart size makes a relatively small contribution to the reduction in this index of LV systolic performance. Thus, standardization for heart size may not be necessary to identify whether preserved or depressed LV chamber elastance exists in an individual adult patient with cardiac pathology compared with normal adult patients.

Adult↗
PubMed1989

Responsiveness of the maximum time-varying elastance to alterations in left ventricular contractile state in man.

This investigation was designed to establish the relative responsiveness of maximum time-varying elastance (Emax) slope values to alterations in left ventricular contractile state in comparison with isovolumic and ejection phase indices in man. Accordingly, nine patients had a bipolar right atrial pacing catheter and micromanometer left ventricular catheter placed and red blood cells tagged with technetium-99m for radionuclide angiography. Hemodynamic measurements and radionuclide angiograms were acquired simultaneously over a range of loading conditions produced by methoxamine or nitroprusside infusions during both the basal and enhanced contractile states. Enhanced left ventricular contractility was produced by a steady-state dobutamine infusion of 2 to 10 mu/kg/min. The mean (+)dP/dtmax increased from 1510 +/- 460 mm Hg/sec during the basal state to 2537 +/- 546 mm Hg/sec (p less than 0.001) during the dobutamine infusion. The mean Emax slope value also increased from 4.34 +/- 1.40 mm Hg/ml during the basal state to 6.41 +/- 1.90 mm Hg/ml (p less than 0.001) during the dobutamine infusion. The average percent change in the Emax slope value (51 +/- 26%) was less than those for the isovolumic indices (57% to 112%), while it was more than those for the ejection phase indices (11% to 53%). When the variability in the percent changes for each of these contractile indices was incorporated into the analysis, the Emax slope values demonstrated a greater responsiveness to changes in left ventricular contractility than did the isovolumic and ejection phase indices. In conclusion, the Emax slope value calculated by this method is a contractile index, which is less affected by measurement variability and the influences of loading conditions than are the isovolumic and ejection phase indices, and therefore may improve our ability to both detect and quantitate changes in left ventricular contractility in man.

Adult↗
PubMed1989

Radionuclide left ventricular contractile indices and their relationship to heart size in dogs.

To identify possible mechanisms to explain differences between the maximum time-varying elastance (Emax) and end-systolic pressure-volume (Ees) slope values calculated with radionuclide angiography and to establish whether they have a relationship to heart size, we studied 16 dogs that were instrumented with micromanometer left ventricular catheters and had red blood cells tagged with technetium-99m for radionuclide angiography. Hemodynamics and radionuclide angiograms were obtained under control conditions and during six additional steady-state loading conditions. Isochronal Emax averaged 7.14 +/- 2.54 mm Hg/ml, while Ees averaged 5.68 +/- 1.88 mm Hg/ml (p less than 0.01), but they were highly correlated (r = 0.95, p less than 0.001). This observation was related to the assumption of linearity when curvilinearity was present and to the important influence of timing on these relationships. The Emax and Ees slope values were compared to dog weight; left ventricular weight, which ranged from 85 to 142 gm (mean 113 +/- 18 gm); and left ventricular end-diastolic volume, which ranged from 15 to 56 ml (mean 29 +/- 10 ml) using multiple regression analyses. The Emax and Ees slope values demonstrated a comparable inverse linear relationship with only left ventricular end-diastolic volume (r = 0.76 and -0.69, p less than 0.001 and p less than 0.01). We conclude that the differences between Emax and Ees slope values calculated with radionuclide angiography are related to the assumption of linearity when curvilinearity is present and to the importance of the timing of systolic events and that both Emax and Ees are comparably related to left ventricular end-diastolic volume.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Load dependence of the single beat maximal pressure (stress)/volume ratios in humans.

To determine whether the slopes of the single beat maximal pressure (stress)/volume ratios are sensitive to changes in loading conditions in humans, 16 patients without cardiac disease were studied with simultaneous micromanometer-determined left ventricular pressures and biplane contrast cineangiograms under control conditions and during methoxamine and nitroprusside infusions. Left ventricular volumes were calculated with use of a Simpson's rule algorithm, wall thickness was obtained iteratively, and both midwall circumferential and meridional stresses were computed frame by frame. The maximal pressure/volume and both circumferential and meridional maximal stress/volume ratios were calculated using a single beat from each loading condition assuming a zero volume-axis intercept. Mean left ventricular systolic pressure increased 47% during the methoxamine infusion and decreased 22% during the nitroprusside infusion compared with control (p less than 0.001 for both). Despite these changes in left ventricular systolic pressure, heart rate was eliminated as a confounding variable by right atrial pacing; and mean maximal rate of change of left ventricular pressure [(+)dP/dtmax] and rate of change at developed pressure 40 mm Hg [(+)(dP/dt) per DP40] values did not differ significantly. Mean single beat maximal pressure/volume ratios also did not differ significantly among the three loading conditions. In contrast, mean single beat circumferential and meridional maximal stress/volume ratios were 3.15 +/- 1.83 and 1.40 +/- 0.82 g/cm2 per ml at control; they increased to 4.47 +/- 2.44 and 2.21 +/- 1.25 g/cm2 per ml during the methoxamine infusion (p less than 0.001 for both), and they decreased during the nitroprusside infusion to 2.58 +/- 1.47 and 1.14 +/- 0.57 g/cm2 per ml (p less than 0.05 and p less than 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Radionuclide determination of the relationship between left ventricular contractile state and ejection fraction.

To determine whether the relationship between various measures of left ventricular (LV) contractile state and ejection fraction (EF) is linear in man, we studied 30 patients during right atrial pacing over a range of loading conditions. With the use of micromanometer LV pressures and radionuclide LV volumes, pressure-volume (P-V) loops were generated for each loading condition. Then isochronal, instantaneous P-V data points were obtained by linear regression analysis to attain the maximum slope (Emax) of these time-varying isochrones. Other measures of LV end systole were also used to calculate end-systolic P-V relations in a similar fashion, and indirect P-V relations were obtained from the linear regression analysis of brachial artery peak pressure vs minimum LV volume data points. When the slopes of these LV contractile measures were compared to the radionuclide LV EFs, the linear correlation coefficients ranged from 0.53 to 0.67. After natural log transformation of the LV contractile state and EF data, the correlation coefficients for the polynomial curve fits ranged from 0.80 to 0.88. When the correlation coefficients for the polynomial curve fits of the natural log transformed data were compared to those for the linear regression analyses of the raw data, significant improvements were evident (p less than 0.05). Thus the relationship between various measures of LV contractile state and EF obtained with radionuclide angiography is best approximated by a complex, curvilinear relationship that is due, in part, to the wide range of LV contractile states within the relatively narrow normal range of LV ejection fractions.

Adult↗
PubMed1988

Assessment of the radionuclide angiographic left ventricular maximum time-varying elastance calculation in man.

This investigation was designed to determine whether left ventricular (LV) maximum time-varying elastance (Emax) calculations obtained using equilibrium radionuclide angiography (RNA) were comparable to those obtained using biplane contrast cineangiography (CINE), and whether simple, indirect P-V relations might provide reasonable, alternative estimates of Emax. Accordingly, we studied 19 patients with simultaneous high-fidelity micromanometer LV and fluid brachial artery (Ba) pressure recordings, CINE, and RNA under control conditions and during methoxamine and nitroprusside infusions. Emax was defined for CINE and RNA as the maximum slope of the linear relation of isochronal, instantaneous P-V data points obtained from each of the three loading conditions. The indirect P-V relations were similarly obtained from Ba peak (P) pressure versus minimum RNA LV volume (BaP/minV) and Ba dicrotic notch (di) pressure versus minimum RNA LV volume (Badi/minV) data points. The mean heart rates and LV (+)dP/dtmax values were minimally altered during the three loading conditions. The isochronal Emax values ranged from 1.40 to 6.73 mmHg/ml (mean 4.13 +/- 1.99 s.d. mmHg/ml) for CINE and from 1.48 to 7.25 (mean 4.35 +/- 1.81 mmHg/ml) for RNA (p = N.S.). Similarly, the unstressed volumes ranged from -10 to 80 ml (mean 30 +/- 23 ml) for CINE and from -8 to 77 ml (29 +/- 21 ml) for RNA (p = N.S.). The individual, isochronal Emax values by RNA correlated with those by CINE (r = 0.86). In 14 of the 19 patients, the BaP/minV and Badi/minV relations correlated with the isochronal Emax values calculated by RNA (r = 0.83 and 0.82, respectively), and these relations also correlated with the Emax values calculated by CINE (r = 0.82 and 0.78, respectively). The slope and V0 values for the BaP/minV and Badi/minV relations underestimated those for Emax by RNA and CINE (p less than 0.01 and p less than 0.05, respectively, for both). Thus, the isochronal Emax values calculated using RNA are comparable to those obtained using CINE in man. Moreover, indirect P-V relations underestimate these Emax values, but they are linearly related with the isochronal Emax values calculated by RNA and CINE. Consequently, these indirect P-V relations may provide a more simple, alternative estimate of LV contractile function in man.

Adult↗
PubMed1987

Variability of quantitative digital subtraction coronary angiography before and after percutaneous transluminal coronary angioplasty.

Quantitative coronary angiography has been proposed as a means of reducing observer variability in the interpretation of coronary angiograms, especially before and after percutaneous transluminal coronary angioplasty (PTCA). Analysis of 13 consecutively acquired biplane digital subtraction angiograms before and after PTCA was undertaken to determine intra- and interobserver variability of absolute lesion diameter, relative videodensitometric cross-sectional area, automated percent diameter stenosis and visual percent diameter stenosis using a new fully automated quantitative computer program. The reliability of single-view measurements was also assessed. Both before and after PTCA, measures of absolute diameter showed less interobserver variability than densitometry, percent automated diameter stenosis and percent visual diameter stenosis measurements (before, r = 0.95, 0.83, 0.86, 0.70; after, 0.95, 0.88, 0.81, 0.62, respectively). Relative videodensitometric cross-sectional area correlated poorly with images from the orthogonal view (r = 0.46). These data suggest that quantitative angiography reduces variability from visual estimates; of all quantitative angiographic measurements, the highest interobserver reproducibility is achieved using absolute lesion diameter both before and after PTCA, probably because no operator interaction is needed to identify a "normal" segment. Unselected, single-view quantitative arteriography is poorly reproducible using videodensitometry. Therefore, automated determination of absolute lesion diameter in at least 2 projections provides the most reproducible evaluation of coronary lesions both before and after PTCA.

Angioplasty, Balloon↗
PubMed1987

Value of tomographic thallium-201 imagining in patients with chest pain following coronary artery bypass grafting.

To determine whether thallium-201 washout profile analysis can detect regional myocardial ischemia caused by coronary artery bypass graft occlusion or progression of disease in nonbypassed coronary arteries, 19 consecutive patients with chest pain following bypass grafting were evaluated with coronary arteriography and thallium-201 scintigraphy. Twenty of the 55 coronary artery regions were perfused by an occluded bypass graft or a significantly stenosed (greater than or equal to 70% diameter narrowing) nonbypassed coronary artery, while 35 coronary regions were perfused by patent bypass grafts or insignificantly diseased coronary arteries. The tomographic thallium-201 washout profile results correlated with the bypass graft and coronary arteriographic findings (k = 0.67, P less than 0.001). The sensitivity of tomographic thallium-201 washout profile abnormalities for arteriographic abnormalities was 75%, while the specificity was 86%. The authors conclude that tomographic thallium-201 washout profile analysis may be very useful in the evaluation of patients with chest pain following coronary artery bypass grafting by detecting regional myocardial ischemia caused by occlusion of specific bypass grafts or progression of disease in nonbypassed coronary arteries.

Adult↗
PubMed1987

Hemodynamically important right ventricular infarction: follow-up evaluation of right ventricular systolic function at rest and during exercise with radionuclide ventriculography and respiratory gas exchange.

The prognosis and recovery of right ventricular systolic function in patients with hemodynamically documented right ventricular myocardial infarction (RVMI) is unclear. Therefore 27 patients who met hemodynamic criteria for RVMI were followed for at least 1 year. Four patients died within 1 year and 23 survived. Postmortem examination performed in three of the four patients showed extensive infarction of the right and left ventricles. Survivors underwent early and late follow-up resting radionuclide ventriculograms and late exercise studies. During long-term follow-up (1 to 4 years) resting radionuclide ventriculography demonstrated a significant improvement in right ventricular ejection fraction (30 +/- 7% to 43 +/- 8%; p less than .001) and right ventricular wall motion index (2.2 +/- 0.4 to 1.5 +/- 0.5; p less than .001) in 18 patients who survived longer than 1 year. Fourteen of these patients underwent upright bicycle exercise while off beta-blocking drugs and peak radionuclide ejection fraction was acquired after anaerobic threshold was achieved. Right ventricular ejection fraction increased significantly from 41 +/- 10% to 47 +/- 12% (p less than .001), as did the left ventricular ejection fraction (55 +/- 15% to 60 +/- 12%; p less than .05). The direction and magnitude of change of the right ventricular ejection fraction correlated significantly with the left ventricular ejection fraction (r = .82, p less than .02). Deviations from this correlation occurred in patients who had a decreased forced expiratory volume in 1 sec and an abnormal ventilatory reserve during exercise.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1987

The relationship of various measures of end-systole to left ventricular maximum time-varying elastance in man.

This investigation was designed to calculate left ventricular maximum time-varying elastance (Emax), to define the relationship between Emax and pressure-volume (P-V) relations at other, more easily defined measured of end-systole, and to determine whether these measures of left ventricular contractile function can be normalized in man. Accordingly, we studied 10 subjects with simultaneous high-fidelity micromanometer left ventricular and ascending aortic pressure recordings and biplane contrast cineangiograms at control conditions and during infusion of methoxamine and nitroprusside. Emax was defined as the maximum slope of the linear relation of isochronal, instantaneous P-V data points obtained from each of the three loading conditions. Left ventricular end-systole was also defined for each loading condition as: the time of the maximum P-V ratio (maxPV), minimum ventricular volume (minPV), (-)dP/dtmin [(-)dP/dtPV], and zero systolic flow approximated by the central aortic dicrotic notch (AodiPV). The mean heart rates and LV (+)dP/dtmax were insignificantly altered during the three loading conditions. Isochronal Emax ranged from 3.38 to 6.73 mm Hg/ml (mean 5.48 +/- 1.23 [SD] mm Hg/ml) and the volume-axis intercepts at zero pressure ranged from -2 to 51 ml (mean 18 +/- 16 ml). The isochronal slope calculations were reproducible (r = .97 to .99). The end-systolic P-V slope values for the maxPV, minPV, (-)dP/dtPV, and AodiPV relations correlated with isochronal Emax (r = .90, .88, .69, and .74, respectively). The average slope values for these end-systolic P-V relations, however, underestimated the mean Emax (p less than .01 to p less than .001). The mean extrapolated volume-axis intercepts for these end-systolic P-V relations also underestimated that for Emax. Finally, the isochronal Emax and other end-systolic P-V relation slope values demonstrated inverse linear relationships with left ventricular mass (r = -.68 to -.91, p less than .05 to p less than .001). Only the Emax volume-axis intercepts showed a linear relationship with left ventricular end-diastolic volume (r = .75). Thus we conclude that the time-varying elastic properties of the left ventricle can be calculated in man, that commonly used end-systolic P-V relations significantly underestimate isochronal Emax, and that normalization of isochronal Emax and other end-systolic P-V relation slope values might be performed in man with left ventricular mass; no obvious relationship between volume-axis intercepts and measures of left ventricular or body size was apparent.

Adult↗