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Biomedical subjects

F G St Goar

Publications and source records attributed to F G St Goar.

At least 37 records · Page 2Linked to original sources
PubMed1994

Feasibility of serial intracoronary ultrasound imaging for assessment of progression of intimal proliferation in cardiac transplant recipients.

BACKGROUND: Serial quantitative coronary angiography is used to assess progression of coronary disease; however, pathology studies have demonstrated angiographic insensitivity for determining atheroma. Intracoronary ultrasound (ICUS) can define and measure the components of the arterial wall and offers the potential for precise quantitative assessment of disease progression on serial examinations. The present study was done to test the feasibility of serially assessing intimal proliferation at the same coronary site with ICUS imaging in cardiac transplant recipients. METHODS AND RESULTS: ICUS imaging was done with a 30-MHz, 5F or 4.3F ultrasound imaging catheter at the time of angiography in 70 cardiac allografts (3.8 sites per patient) initially and 1 year later. Mean intimal thickness (IT), luminal area (LA), and total area (TA) of lumen plus intima and an index of intimal thickness (II = TA - LA/TA) were measured at each site. Additionally, vessels were graded using a scale incorporating criteria of intimal thickness and circumferential involvement. Side-by-side comparisons of paired angiograms were performed both to verify the similarity of ICUS imaging site and to detect new angiographic abnormalities. At least one site could be assessed serially by ICUS in 100% of patients, but only 189 of the original 263 coronary sites (72%) (2.7 sites per patient) could be matched satisfactorily on the second study. Thirty-nine patients (56%) had mild IT and 31 patients (44%) had moderate or severe IT on the initial study. Both groups showed the same IT progression the following year (delta = 0.05 +/- 0.13 versus 0.07 +/- 0.15 mm; P = NS). Twenty-seven of the 70 patients (39%) showed progression by ICUS. The 23 patients with ICUS progression and angiographically normal vessels had the same progression in intimal thickening as the 4 patients with ICUS progression but showing angiographic disease (delta = 0.17 +/- 0.13 versus 0.22 +/- 0.10 mm; P = NS). CONCLUSIONS: Replication of the intracoronary imaging site by judgment of two observers at an initial study and at a second study 1 year later was possible in at least one vessel site in 100% of the 70 patients and in 72% (189 of 263) of the original imaging sites (2.7 sites per patient). Serial ICUS demonstrates progression of intimal thickening at specific sites in only some cardiac transplant patients. Progression of intimal proliferation can occur in individuals in the presence or absence of initially increased intimal thickening or of angiographic disease at the time of the initial studies. Angiography is insensitive for recognizing early intimal thickening of the coronary vessels.

Adolescent↗
PubMed1994

Interventional strategies for managing acute myocardial infarction.

The management of acute myocardial infarction has evolved greatly with the development of interventional cardiology and thrombolytic therapy. Interventional strategies in the setting of thrombolytic therapy include immediate, delayed, and elective PTCA. Randomized trials suggest no benefit to these approaches; however, primary PTCA without adjunctive lytics when compared to lytic therapy alone may improve both survival and costs. Newer catheter-based technology may also enhance outcomes in patients with acute myocardial infarction.

Angioplasty, Balloon, Coronary↗
PubMed1993

Coronary artery size and dilating capacity in ultradistance runners.

BACKGROUND: Increases in coronary artery size and dilating capacity have been observed in some animals after endurance training, and at autopsy, active men appear to have enlarged epicardial coronary arteries. This cross-sectional study was designed to test the hypothesis that highly trained endurance runners have larger epicardial coronary arteries and greater dilating capacity than inactive men. METHODS AND RESULTS: The subjects, ages 39-66 years, included 11 male volunteers who had participated in ultradistance running during the past 2 years and 11 physically inactive men who had been referred for arteriography but had no visible coronary artery disease. The internal diameter of the proximal segments of each major epicardial coronary artery was measured before and after nitroglycerin administration using a computer-based quantitative arteriographic analysis system. Measurements also included maximal oxygen uptake, plasma lipoprotein concentrations, body composition, and cardiac mass by echocardiography. Before nitroglycerin, the sum of the cross-sectional areas for the proximal right, left anterior descending, and circumflex arteries was not different for the runners and the inactive men: 22.7 +/- 4.79 versus 21.0 +/- 7.97 mm2 (p = 0.57), respectively. However, the increase in the sum of the cross-sectional area for the proximal right, left anterior descending, and circumflex arteries in response to nitroglycerin was greater for the runners (13.20 +/- 4.76 versus 6.00 +/- 3.02 mm2; p = 0.002). Left ventricular mass index (152 +/- 21 versus 116 +/- 41 g/m2; p < 0.05) but not left ventricular mass (284 +/- 40 versus 246 +/- 91 g; p = 0.22) was significantly greater for the runners. Among the runners, dilating capacity was positively correlated with aerobic capacity and negatively related to adiposity, resting heart rate, and plasma lipoprotein concentrations. CONCLUSIONS: Highly trained, middle-aged endurance runners demonstrated a significantly greater dilating capacity of their epicardial coronary arteries in response to nitroglycerin compared with inactive men. The causes of this greater dilating capacity and its clinical significance need to be determined.

Adult↗
PubMed1993

Immediate and one-year safety of intracoronary ultrasonic imaging. Evaluation with serial quantitative angiography.

BACKGROUND: Intracoronary ultrasound (ICUS) has the ability to quantitatively evaluate vessel wall morphology and is well suited for serial studies of coronary artery disease regression and progression. However, the potential risk for catheter-induced endothelial damage and accelerated atherosclerosis in instrumented vessels is a concern. The acute effects as well as the 1-year safety of ICUS regarding its impact on the atherosclerotic process were assessed. METHODS AND RESULTS: The acute studies include 240 intracoronary studies performed in 170 cardiac transplant recipients. Patients were systematically heparinized. Only vessels > or = 2 mm in diameter were visualized. Coronary arteries of 38 patients were measured by quantitative coronary angiography in matched angiograms at an interval of 1 year after the initial ICUS examination was performed to assess long-term effects. The angiographic measurements in the previously instrumented and noninstrumented vessels were compared. Forty-nine vessels that had been imaged (IM) in these 38 patients with a 5F ICUS catheter were compared with 61 vessels not previously imaged (NIM) in the same patients. Absolute and percentage change in angiographically measured mean vessel diameters in the ICUS imaged and nonimaged segments were compared. Despite pretreatment with nitroglycerin, 20 patients (8.3%) had angiographically evident coronary spasm. In all cases, this was reversed by giving nitroglycerin. One year after the original imaging study, no difference was noted between imaged and nonimaged vessels in change in absolute vessel diameter (IM, -0.11 +/- 0.28 mm vs NIM, -0.07 +/- 0.22 mm; P = .49) or in percentage change in diameter (IM, -5 +/- 11% vs NIM, -3 +/- 7%; P = .32). CONCLUSIONS: Intracoronary ultrasound in cardiac transplant recipients was associated with no clinical morbidity and a low incidence of vessel spasm in large and medium-size coronary arteries. It does not accelerate progression of angiographically quantifiable coronary artery disease. This study suggests that ICUS can be safely used even in coronary arteries not undergoing interventions.

Cardiac Catheterization↗
PubMed1992

Systemic venous flow during cardiac surgery examined by intraoperative transesophageal echocardiography.

Patterns of systemic venous return change after cardiac surgery. However, the exact timing and underlying mechanisms are not well understood. To analyze these changes transesophageal echocardiography was used to evaluate 21 patients (mean age 56 +/- 17 years) during cardiac surgery. Eleven patients underwent coronary bypass grafting, 2 had ablation of accessory bundles, 4 had mitral and 4 had aortic valve replacements. All were in sinus rhythm and were undergoing their first cardiac operation. Hepatic and pulmonary venous flow, tricuspid annular motion, and signs of tricuspid regurgitation were recorded sequentially 5 times: (A) with chest closed, (B) with chest open and pericardium closed, (C) with both chest and pericardium open, (D) after cardiopulmonary bypass with chest open, and (E) after cardiopulmonary bypass with chest closed. The hepatic venous Doppler flow velocity integrals (cm) changed, from stage A to stage E: systolic flow decreased from 5.9 +/- 5.2 to 2.2 +/- 1.4 (p less than 0.01); diastolic flow increased from 3.1 +/- 1.5 to 4.8 +/- 3.3 (p less than 0.001); and systolic to diastolic ratio decreased from 2.0 +/- 1.2 to 0.7 +/- 0.6 (p less than 0.001). Reversed flow at the end of ventricular systole was present in 9 patients (43%) at stage A and in all patients at stage E. Decreased tricuspid annular motion was noted in all but 1 patient after cardiopulmonary bypass. No patient presented significant tricuspid regurgitation at any stage. In conclusion, the significant change in the pattern of systemic venous return after open heart surgery is not due to opening of the chest wall or parietal pericardium, or to tricuspid regurgitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1992

Nitroglycerin-induced coronary vasodilation in cardiac transplant recipients. Evaluation with in vivo intracoronary ultrasound.

BACKGROUND: Coronary artery vasomotion is altered after cardiac transplantation. The impact of accelerated transplant coronary atherosclerosis and myocardial rejection on vasomotion is not well understood. Intravascular ultrasound is a new imaging method with the ability to study real-time changes in coronary artery dimensions. METHODS AND RESULTS: Epicardial coronary artery response to nitroglycerin was studied in 32 cardiac transplant recipients (age, 47 +/- 11 years) 3 weeks to 10 years after transplantation with intracoronary ultrasound. Cross-sectional luminal area and diameter were measured at a fixed position in the left anterior descending artery immediately before and every 30 seconds for 5 minutes after 0.4 mg of sublingual nitroglycerin. Cross-sectional area increased from a baseline of 13.1 +/- 3.9 mm2 to 15.8 +/- 3.9 mm2 at maximal vasodilation; luminal diameter increased from 4.0 +/- 0.6 mm to 4.5 +/- 0.6 mm. This increase reached statistical significance (p less than 0.001) at 1.5 minutes after administration of nitroglycerin; mean maximum increase occurred at 4.5 minutes (24% for cross-sectional area and 11% for luminal diameter). Patients with biopsy-proven mild or moderate concurrent rejection had a significantly blunted vasodilatory response versus the nonrejection group (9% versus 27% for cross-sectional area, p less than 0.04), although a vasodilatory effect was still present. Nitroglycerin response was well preserved in patients up to 10 years after transplantation; however, there was a trend toward a decreased response in patients studied immediately after transplantation (21% versus 29%, p = 0.37). Coronary intimal thickness, as measured by ultrasound, had no impact on the vasodilatory response (R = 0.23, p = 0.34). CONCLUSIONS: Vasodilatory response to nitroglycerin in cardiac transplant recipients is attenuated during episodes of cardiac rejection. This response is preserved in long-term survivors and is independent of the degree of intimal thickening. Intravascular ultrasound provides a new method to document real-time epicardial coronary vasomotion.

Adult↗
PubMed1992

Intracoronary ultrasound in cardiac transplant recipients. In vivo evidence of "angiographically silent" intimal thickening.

BACKGROUND: Accelerated coronary atherosclerosis is a major factor limiting allograft longevity in cardiac transplant recipients. Histopathology studies have demonstrated the insensitivity of coronary angiography for detecting early atheromatous disease in this patient population. Intracoronary ultrasound is a new imaging technique that provides characterization of vessel wall morphology. The purpose of this study was to compare in vivo intracoronary ultrasound with angiography in cardiac transplant recipients. METHODS AND RESULTS: The left anterior descending coronary artery was studied with intracoronary ultrasound in 80 cardiac transplant recipients at the time of routine screening coronary angiography 2 weeks to 13 years after transplantation. A mean and index of intimal thickening were obtained at four coronary sites. Intimal proliferation was classified as minimal, mild, moderate, or severe according to thickness and degree of vessel circumference involved. Twenty patients were studied within 1 month of transplantation and had no angiographic evidence of coronary disease. An intimal layer was visualized by ultrasound in only 13 of these 20 presumably normal hearts. The 60 patients studied 1 year or more after transplantation all had at least minimal intimal thickening. Twenty-one patients (35%) showed minimal or mild, 17 (28%) moderate, and 21 (35%) severe thickening. Forty-two of these 60 patients had angiographically normal coronary arteries, 21 (50%) of whom had either moderate or severe thickening. All 18 patients with angiographic evidence of coronary disease had moderate or severe intimal thickening, but there was no statistically significant difference in intimal thickness or index when compared with the patients with moderate or severe proliferation and normal angiograms (thickness, 0.53 +/- 0.35 mm versus 0.64 +/- 0.30 mm, p = NS; index, 0.28 +/- 0.10 versus 0.34 +/- 0.10, p = NS). CONCLUSIONS: The majority of patients 1 or more years after cardiac transplantation have ultrasound evidence of intimal thickening not apparent by angiography. Intracoronary ultrasound offers early detection and quantitation of transplant coronary disease and provides characterization of vessel wall morphology, which may prove to be a prognostic marker of disease.

Coronary Angiography↗
PubMed1992

Intravascular ultrasound imaging of coronary arteries. Is three layers the norm?

BACKGROUND: The purpose of this study was to evaluate the significance of the three-layered appearance of coronary arteries in adolescence and adults from intravascular ultrasound scans and to correlate these observations with histopathology. METHODS AND RESULTS: Sixteen intact hearts were excised at autopsy from patients with no clinical history of coronary artery disease. The patients' ages ranged from 13 to 55 years. A 30-MHz ultrasound imaging catheter was used to obtain images throughout the epicardial coronary vasculature. A total of 72 image cross sections was marked by epivascular sutures, and the corresponding histological sections were examined. Ultrasound images were classified into two groups: images exhibiting three-layered appearance and images without distinct layering. Histological analysis revealed a significantly greater degree of intimal thickening in segments with three layers (243 +/- 105 microns) than in nonlayered segments (112 +/- 55 microns). Discriminant analysis of these data predicted the threshold between the two groups to be 178 microns. Measurements of medial thickness were not different between these two groups (235 +/- 61 versus 210 +/- 76 microns). In the nonlayered group, the average patient age was 27.1 +/- 8.5 years, whereas in the three-layered groups, the average age was 42.8 +/- 9.8 years. CONCLUSIONS: The intracoronary ultrasound image appearance of young, morphologically normal coronary artery walls is homogeneous without layering. A three-layered appearance suggests the presence of at least 178 microns of intimal thickening and is seen more frequently with advancing age.

Adolescent↗
PubMed1992

Detection of coronary atherosclerosis in young adult hearts using intravascular ultrasound.

BACKGROUND: Coronary atherosclerosis has been demonstrated in young adults by postmortem pathology. Angiographic evaluation of coronary disease in young adults is limited by ethical issues and the insensitivity of angiography for detecting early pathology. Catheter-based intracoronary ultrasound has proven useful both in detecting and quantitating coronary disease, but the ultrasound appearance of young, angiographically normal, coronary arteries has not been well defined. METHODS AND RESULTS: Twenty-five subjects were examined with intracoronary ultrasound within 1 month of cardiac transplantation. Mean age of the donor hearts was 28 years (range, 14-43 years). Measurements of an index of intimal thickening were obtained at four left anterior descending coronary artery sites in each patient. All study patients had angiographically normal coronary arteries. Ultrasound in 14 subjects demonstrated a three-layered appearance of the coronary vessel wall with a mean intimal index of 0.16 +/- 0.07. The other 10 subjects, including all donors under the age of 25 years, had coronary vessel wall layers too thin to be imaged separately at the 30-MHz sound frequency. Five subjects had ultrasound evidence of focal intimal thickening greater than 500 microns. The donors of these hearts each had risk factors for coronary artery disease. Two subjects died within 5 weeks of their ultrasound study. Histological measurements of the vessel wall layers were similar to the corresponding ultrasound values. CONCLUSIONS: This study provides a reference for the intravascular ultrasound appearance of young adult coronary arteries and confirms pathology findings that young subjects with angiographically normal vessels have a range of coronary intimal thickening, which includes occasional evidence of focal, early atheromatous lesions.

Adult↗
PubMed1992

Contributors of characteristic mitral flow velocity pattern in congestive heart failure--from clinical observations back to experimental validations.

Mitral flow velocity pattern in patients with left ventricular (LV) diastolic dysfunction usually includes decreased peak early diastolic filling velocity (E), slowed deceleration of the early diastolic filling wave and increased peak filling velocity at atrial contraction (A). However, the abnormal mitral flow velocity pattern can be normalized in the presence of concomitant congestive heart failure. In such cases E can be equal to or even higher than normal, its deceleration is normal or faster than normal value, and A can be normal or lower than normal value. Clinical observations in patients with severe heart failure showed that the mitral flow velocity pattern changes with vasodilating therapy, reflecting the changes in the left atrial (LA) to LV pressure difference rather than those in the absolute LA pressure or LV pressure alone. This was validated in the canine study in which levels of LV dysfunction were made by the injection of microspheres into the left coronary artery to study the interrelation among the mitral flow velocity pattern and LA and LV pressures. In this experiment, the changes in the mitral flow velocity pattern could not be explained by the changes in LA or LV pressure alone but was better explained by the changes in the LA to LV pressure difference. Not only LA-LV crossover pressure but also LA compliance seem to be important as determinants of LA pressure level in diastole. In addition to LV relaxation rate, incompleteness of relaxation, elastic recoil and LV passive elastic properties, extracardiac constraint is also considered to be an important determinant of the level of the LV diastolic pressure and hence of the mitral flow velocity pattern at least in the presence of congestive heart failure. Thus, mitral flow velocity pattern is determined by the interaction of LA and LV pressures, both of which are affected by chamber properties as well as loading conditions.

Animals↗
PubMed1991

Hepatic venous flow assessed by transesophageal echocardiography.

Systemic venous flow patterns are easily assessed by transthoracic echocardiography for evaluation of right heart dynamics. However, the transthoracic approach cannot be used in patients undergoing thoracic surgery. The present study describes a method for obtaining hepatic venous flow velocity with transesophageal Doppler echocardiography. Twenty-nine patients were studied with transthoracic echocardiography just before cardiac surgery and with transesophageal echocardiography during surgery. Hepatic venous flow velocity recordings were obtained in 14 of 29 patients with the transthoracic and in all 29 with the transesophageal approach. Timing of flow pattern was similar with the two methods, but recordings obtained with transesophageal echocardiography were inverted compared with those obtained with transthoracic echocardiography as a result of the difference in probe location in relation to flow direction. The time-velocity integrals obtained with the two techniques did not differ significantly; for the transthoracic and transesophageal approaches, they were, respectively, 7.3 +/- 3.4 versus 5.7 +/- 4.4 for systolic flow; 1.0 +/- 1.0 versus 0.5 +/- 0.6 for end-systolic flow reversal; 4.7 +/- 2.3 versus 3.7 +/- 1.7 for diastolic flow; 2.0 +/- 1.8 versus 1.5 +/- 1.5 for atrial flow reversal and 1.9 +/- 1.0 versus 1.7 +/- 1.1 for systolic/diastolic ratio. In conclusion, hepatic venous flow values are obtained more frequently and with better quality by transesophageal than by transthoracic echocardiography. The flow patterns and velocity integrals are similar with both methods and previous experience with transthoracic echocardiography should be applicable to the transesophageal technique. Transesophageal Doppler echocardiography therefore has potential for studying right heart dynamics during anesthesia and surgery.

Anesthesia, General↗
PubMed1991

Intravascular ultrasound imaging of angiographically normal coronary arteries: an in vivo comparison with quantitative angiography.

Intravascular ultrasound, a new technique for real-time two-dimensional visualization of arteries and veins, delineates vessel wall morphology and measures luminal dimensions. This imaging method has been validated with in vitro systems and in peripheral vessels, but there are few in vivo coronary artery studies. Twenty cardiac transplant recipients with no angiographic coronary artery disease were scanned with a 30-MHz intravascular ultrasound catheter from the left main coronary ostium to the mid-left anterior descending coronary artery. Simultaneous angiographic measurements were performed at 76 sites. Ultrasound end-diastolic diameters in two perpendicular axes were 3.8 +/- 0.9 and 3.9 +/- 0.6 mm, respectively, and mean diameter derived from an area determined by planimetry was 3.9 +/- 0.9 mm. Angiographic coronary artery diameters measured with a computer-assisted edge detection system perpendicular to the long axis of the vessel and to the long axis of the catheter were 3.4 +/- 0.8 and 3.6 +/- 0.8 mm, respectively. Luminal diameters measured with the two imaging systems correlated closely, with an r value of 0.86 when ultrasound was compared with the angiographic diameter measured perpendicular to the vessel and 0.88 when compared with the angiographic diameter measured perpendicular to the imaging catheter. Eighty-three percent of the ultrasound-measured diameters were above the line of identity when compared with the simultaneous angiographic measurement. The more the imaging catheter deviated from the long axis of the vessel, the greater was the discrepancy between the ultrasound and angiographic measurements.(ABSTRACT TRUNCATED AT 250 WORDS)

Angiography↗
PubMed1991

Abnormal right heart filling after cardiac surgery: time course and mechanisms.

OBJECTIVE: To study the time course and underlying mechanisms of right heart filling after cardiac surgery. DESIGN: A prospective observational study of adult patients undergoing cardiac surgery. SETTING: Echocardiography laboratory of the Stanford University Medical Center. PATIENTS: Twenty six patients (mean age 54.9) undergoing cardiac surgery were studied before and two days, one week, six weeks, and six months after cardiac surgery. MAIN OUTCOME MEASURES: Flow in the hepatic veins and superior vena cava, tricuspid and mitral annulus motion, signs of tricuspid regurgitation, and right ventricular size were assessed by echocardiography. RESULTS: Right heart filling, expressed as the ratio of systolic to diastolic forward flow Doppler velocity integrals in the superior vena cava and by tricuspid annulus motion, decreased in parallel from before surgery baseline values of 3.5 (SD 3.1) and 21.9 (3.4) mm, respectively to 0.2 (0.1) and 8.1 (2.3) mm two days after operation. A gradual increase towards baseline values was noted after six months, to 1.4 (1.3) and 15.1 (2.3) mm respectively; however, these values were still significantly less than those before operation. Similar changes were seen in the hepatic venous flow pattern. The decrease in total tricuspid annulus motion was most pronounced in its lateral segment and the atrial component of the tricuspid annulus motion showed similar changes. CONCLUSIONS: The pronounced decrease in tricuspid annulus motion during the early postoperative period suggests right atrial and right ventricular dysfunction as mechanisms responsible for the early changes seen. The progressive return to a normal venous filling pattern and the partial recovery of annular motion six months after operation further support the influence of the above mechanisms, as well as their resolution with time. The persistent flow abnormalities and compromised motion of the free aspects of the tricuspid annulus, however, suggest long term tethering of the right heart wall.

Adult↗
PubMed1990

Effects of nitroprusside on transmitral flow velocity patterns in extreme heart failure: a combined hemodynamic and Doppler echocardiographic study of varying loading conditions.

To explore the mechanisms of change of left ventricular diastolic filling associated with preload and afterload reduction, the influence of nitroprusside on the transmitral flow velocity pattern, pulmonary capillary wedge pressure and left ventricular pressure interaction was studied in 11 patients with end-stage heart failure. Pulsed Doppler echocardiographic recordings of mitral inflow were obtained with simultaneous high fidelity left ventricular and phase-corrected pulmonary capillary wedge pressure recordings before and during levels of nitroprusside infusion. With nitroprusside, left ventricular systolic and end-diastolic pressures decreased by 14% and 41% (p less than 0.05, p less than 0.05), respectively, and cardiac output increased by 67% (p less than 0.05). The pulmonary capillary wedge-left ventricular crossover pressure decreased by 41% (p less than 0.05), but the time constant of isovolumetric left ventricular pressure decrease T was insignificantly changed. Isovolumetric relaxation time and acceleration and deceleration times of the early diastolic filling wave were significantly prolonged with nitroprusside infusion (p less than 0.05, p less than 0.05 and p less than 0.05, respectively). Peak early diastolic filling velocity was maintained (65 +/- 11 to 62 +/- 13 cm/s, p = NS) in spite of the decreased absolute crossover pressure. Changes in peak early diastolic filling velocity correlated weakly with changes in the crossover pressure (r = 0.48, p less than 0.05) and correlated better with the crossover to left ventricular minimal pressure difference (r = 0.78, p less than 0.05). Peak early diastolic filling velocity appears to be most affected by the early diastolic pulmonary capillary wedge to left ventricular pressure difference rather than the absolute pulmonary capillary wedge pressure. The lack of peak flow velocity change during nitroprusside infusion could be explained by either the associated decrease in left ventricular minimal pressure or downward shift of left ventricular diastolic pressure by the same amount as the decrease in pulmonary capillary wedge pressure. This may reflect a reduction of external constraint to ventricular distensibility produced by a reduction in filling volume in patients with a markedly dilated ventricle. Thus, a prolonged early diastolic filling period and preserved peak early diastolic filling velocity in spite of decreased left ventricular filling pressure and constant relaxation rate are associated with the beneficial effects of nitroprusside on left ventricular function in patients with severe congestive heart failure.

Blood Flow Velocity↗
PubMed1989

Ultrasonic tissue characterization of human hypertrophied hearts in vivo with cardiac cycle-dependent variation in integrated backscatter.

Integrated ultrasonic backscatter (IB) is a noninvasive measure of the acoustic properties of myocardium. Previous experimental studies have indicated that altered acoustic properties of the myocardium are reflected by the magnitude of variation of IB during the cardiac cycle. In our study, cardiac cycle-dependent variation of IB was noninvasively measured using a quantitative IB imaging system in 12 patients with uncomplicated pressure-overload hypertrophy and 13 patients with hypertrophic cardiomyopathy. Sixteen normal subjects served as a control. The magnitude of cardiac cycle-dependent variation of IB for the posterior wall was 6.0 +/- 0.9 dB in normal subjects, 5.7 +/- 0.8 dB in the patients with uncomplicated pressure-overload hypertrophy, and 6.7 +/- 2.1 dB in the patients with hypertrophic cardiomyopathy. There were no significant differences among any of these groups. In contrast, the magnitude of cardiac cycle-dependent variation of IB for the septum was significantly smaller in the patients with uncomplicated pressure-overload hypertrophy (2.8 +/- 1.3 dB) and in the patients with hypertrophic cardiomyopathy (3.1 +/- 2.3 dB) than in normal subjects (4.9 +/- 1.0 dB). The magnitude of cardiac cycle-dependent variation of IB was smaller as the wall-thickness index increased (r = -0.53, p less than 0.01, n = 82 for all data). This IB measure also correlated with percent-systolic thickening of the myocardium (r = 0.67, p less than 0.01, n = 82). Thus, alteration in the magnitude of cardiac cycle-dependent variation of IB was observed in hypertrophic hearts and showed apparent regional myocardial differences.

Adult↗
PubMedDate not supplied

Left ventricular diastolic dysfunction in end-stage dilated cardiomyopathy: simultaneous Doppler echocardiography and hemodynamic evaluation.

Left ventricular diastolic dysfunction is an integral component of end-stage dilated cardiomyopathy. To better characterize this disorder we studied 15 patients undergoing catheterization during cardiac transplant screening evaluation. Pulsed-wave Doppler echocardiographic recordings of mitral inflow were obtained with simultaneous high-fidelity left ventricular and phase-corrected pulmonary capillary wedge pressures. Doppler-derived isovolumic relaxation times were within normal limits, despite a prolonged coefficient of relaxation (tau), and correlated with pulmonary capillary wedge--left ventricular crossover pressure. Peak velocity of early diastolic filling was similar to that reported in normal subjects and did not correlate with crossover pressure or tau. Early diastolic acceleration and deceleration times were shortened compared with reported normal values. Acceleration time correlated with mean negative dP/dt from mitral valve opening to left ventricular minimum pressure and with crossover pressure, and deceleration time correlated with mean dP/dt from left ventricular minimum pressure to the peak of the rapid filling wave. Late diastolic filling at atrial contraction was absent in 12 patients, all of whom had a significant early diastolic rapid filling wave and an elevated end-diastolic pressure. Despite an increase in pulmonary capillary wedge pressure during atrial contraction, the failing ventricles were unable to generate detectable forward transmitral flow. Poor cardiac pump function was shown by low left ventricular stroke volume, which correlated with the diastolic flow velocity integral. Thus, in end-stage cardiomyopathy, the transmitral flow velocity pattern is characterized by normal peak early filling velocity, low normal isovolumic relaxation time, shortened acceleration and deceleration times of early diastolic flow, decreased early flow velocity integral, and absent or decreased filling during atrial contraction. This pattern reflects interaction between elevated transmitral driving pressure and the compromised relaxation and compliance of a left ventricle functioning on an elevated pressure-volume curve.

Adult↗
PubMedDate not supplied

Port-access bilateral internal mammary artery grafting for left main coronary artery disease: canine feasibility study.

BACKGROUND: To extend the applications of minimal access cardiac surgery, an endovascular cardiopulmonary bypass (CPB) system that allows cardioplegia delivery and cardiac venting was used to perform bilateral internal mammary artery (IMA) bypass grafting in six dogs. METHODS: The left IMA (LIMA) was taken down thoracoscopically from three left lateral chest ports, followed by the right IMA (RIMA) from the right side. One left-sided port was extended medially 5 cm with or without rib resection, to expose the pericardium. Both IMAs were divided and exteriorized through the left anterior mediastinotomy. Flow and pedicle length were satisfactory in all cases. Femoral-femoral bypass was used and the heart arrested with antegrade delivery of cardioplegic solution via the central lumen of a balloon catheter inflated to occlude the ascending aorta. All anastomoses were made through the mediastinotomy under direct vision. In five studies the RIMA was attached to the left anterior descending artery (LAD) and the LIMA to the circumflex, and in one study the RIMA was tunneled through the transverse sinus to the circumflex and the LIMA was anastomosed to the LAD. All animals were weaned from CPB in sinus rhythm without inotropes. CPB duration was 108 +/- 27 minutes (mean +/- SD) and the clamp duration was 54 +/- 10 minutes. RESULTS: Preoperative and postoperative cardiac outputs were 2.9 +/- 0.71/min and 2.4 +/- 0.31/min, respectively (p = NS), and corresponding pulmonary artery occlusion pressures were 6 +/- 3 mmHg and 7 +/- 2 mmHg, respectively (p = NS). All 12 grafts were demonstrated to be fully patent. Postmortem examination revealed well aligned pedicles and correctly grafted target vessels. CONCLUSION: This canine model demonstrates the potential for a less invasive approach to the surgical management of left main coronary artery disease in humans.

Animals↗