Biomedical subjects

E Botvinick

Publications and source records attributed to E Botvinick.

At least 19 recordsLinked to original sources

PubMed2000

Impact of a home-based walking and resistance training program on quality of life in patients with heart failure.

Patients with heart failure (HF) often have profound activity limitations and diminished quality of life (QOL) due to symptoms of dyspnea and fatigue. Although recent studies demonstrate positive physiologic and psychological benefits of low to moderate intensity, supervised, aerobic exercise training performed 3 to 5 days/ week for 20 to 40 minutes' duration, in a monitored setting, the efficacy of a home-based exercise program combining endurance and resistance exercise on symptoms and QOL, are unknown. This randomized controlled study examined the efficacy, safety, and adherence rates of a 3-month home-based combined walking and resistance exercise program on symptoms and QOL in 40 women and men aged 30 to 76 years with New York Heart Association class II to III HF. Baseline and 3-month evaluations consisted of a chronic HF questionnaire to assess symptoms and QOL and exercise capacity by symptom-limited treadmill exercise test with respiratory gas analysis. The exercise intervention improved fatigue (p = 0.02), emotional function (p = 0.01), and mastery (p = 0.04). Overall exercise adherence was excellent (90%) and there were no reported adverse events. A moderate intensity home-based combined walking and resistance program for patients with class II to III HF is safe and effective in reducing symptoms and improving QOL.

Adult↗

PubMed1996

Cardiac activation mapping by MRI.

To establish cardiac MRI as a tool for noninvasive evaluation of activation patterns, 10 healthy volunteers were examined by cine segmented turboFLASH imaging sequences. Sequence modifications for low signal blood-pool appearance were applied, i.e., bilateral spatial saturation for segmented turboFLASH imaging. Pixelwise calculation of first-harmonic Fourier phase values (displayed as color-encoded maps) reveal either anterior septal or left ventricular free-wall sites as areas of earliest phase spreading towards posterior paraseptal sites in segmented turboFLASH scans. Phase scatter is lower in unsaturated than spatially presaturated segmented turboFLASH studies. Phase standard deviation in areas of endocardial displacement is higher in basal than apical slice positions in these scans. Early results indicate that first-harmonic Fourier phase analysis of cardiac-segmented turboFLASH MRI cine studies may provide a tool for noninvasive studies of cardiac activation sequence.

Adult↗

PubMed1995

Adenosine-induced coronary vasodilation during transesophageal Doppler echocardiography. Rapid and safe measurement of coronary flow reserve ratio can predict significant left anterior descending coronary stenosis.

BACKGROUND: Less invasive methods are replacing traditional invasive means of measuring coronary flow reserve (CFR). Transesophageal echocardiography (TEE) is becoming a useful tool for evaluation of coronary artery disease and has recently been used to measure CFR. This has always been done using dipyridamole, but adenosine has a greater vasodilator potency and more favorable kinetics than dipyridamole. This study was done to evaluate the hypothesis that adenosine is safe, rapid, and accurate in measuring coronary blood flow reserve by TEE Doppler. METHODS AND RESULTS: Forty-nine patients who had recently undergone angiography had a transesophageal echocardiogram with visualization of the coronary arteries and measurement of blood flow velocity in the left anterior descending coronary artery (LAD) during adenosine infusion of 0.14 mg/kg per minute. Angiograms were analyzed by quantitative coronary angiography, and significant stenosis was defined as > 70% lumenal diameter narrowing. Thirty-nine of the 49 patients did not have a significant LAD stenosis (group 1); the remainder had significant disease (group 2). Good spectral Doppler recordings of blood flow velocity in the LAD were obtained in 41 of 46 patients (89%). There were no significant differences in baseline coronary blood flow velocities between the two groups. Hyperemic to baseline flow ratios were significantly higher in patients without significant LAD stenosis for peak (2.83 +/- 1.04 versus 1.78 +/- 0.36) and mean (2.68 +/- 0.96 versus 1.75 +/- 0.39) diastolic velocity. A CFR ratio > 2.1 had a sensitivity of 86%, a specificity of 79%, a positive predictive value of 46%, and a negative predictive value of 96% for the absence of critical LAD stenosis. The infusion was well tolerated. It had to be prematurely terminated in only 3 patients (6.5%), and they were asymptomatic. No patient experienced chest pain, palpitations, or flushing. Intraobserver and interobserver variabilities were low, and reproducibility of data was good (< 4%). CONCLUSIONS: Adenosine Doppler TEE is an effective, rapid, safe, and superior means of measuring CFR ratio. This method is convenient for serial measurements of CFR as well as in clinical settings such as evaluation of syndrome X, cardiomyopathy, and aortic regurgitation.

Adenosine↗

PubMed1994

Effects of long-term right ventricular apical pacing on left ventricular perfusion, innervation, function and histology.

OBJECTIVES: The purpose of this study was to better understand the effects of long-term right ventricular pacing on left ventricular perfusion, innervation, function and histology. BACKGROUND: Long-term right ventricular apical pacing is associated with increased congestive heart failure and mortality compared with atrial pacing. The exact mechanism for these changes is unknown. In this study, left ventricular perfusion, sympathetic innervation, function and histologic appearance after long-term pacing were studied in dogs in an attempt to see whether basic changes might be present that might ultimately be associated with the adverse clinical outcome. METHODS: A total of 24 dogs were studied. Sixteen underwent radiofrequency ablation of the atrioventricular (AV) junction to produce complete AV block. Seven of these underwent long-term pacing from the right ventricular apex (ventricular paced group), and nine had atrial and right ventricular apical pacing with AV synchrony (dual-chamber paced group). A control group of eight dogs had sham ablations with normal AV conduction. These dogs had atrial pacing only. Regional perfusion and sympathetic innervation were studied in all dogs by imaging with thallium-201 and [I123]metaiodobenzylguanidine, respectively. The degree of innervation was also determined by assay of tissue norepinephrine levels. Left ventricular function was assessed by radionuclide ventriculography. Cardiac histology was studied with both light and electron microscopy. RESULTS: Mismatching of perfusion and innervation in the ventricular paced group was noted, with perfusion abnormalities of both the septum and free wall. Regional [I123]metaiodobenzylguanidine distribution was homogeneous. Tissue norepinephrine levels were elevated in both the ventricular and dual-chamber paced groups compared with the control group. No light or electron microscopic findings were noted in any groups. In the dual-chamber paced group, diastolic dysfunction was noted, with normal systolic function. CONCLUSIONS: Ventricular pacing resulted in regional changes in tissue perfusion and heterogeneity between perfusion and sympathetic innervation. Both ventricular and dual-chamber pacing were associated with an increase in tissue catecholamine activity. The abnormal activation of the ventricles via right ventricular apical pacing may result in multiple abnormalities of cardiac function, which may ultimately affect clinical outcome.

3-Iodobenzylguanidine↗

PubMed1993

Assessment of perfused left ventricular mass in normal, ischemic, and reperfused myocardium by means of single-photon emission computed tomography of technetium-99m isonitrile.

To test the hypothesis that single-photon emission tomography of technetium (Tc) 99m hexakis 2-methoxyisobutyl isonitrile (Tc-MIBI) can accurately measure perfused left ventricular (LV) mass in nonischemic, ischemic, and reperfused myocardium, we acquired Tc-MIBI tomographic images in canines with normally perfused hearts (n = 33) after occlusion of the left anterior descending coronary artery (n = 15), after reperfusion (n = 13), and with subsequent second injection of Tc-MIBI (15 to 18 mCi; n = 12). In all ischemic studies the initial dose of Tc-MIBI (5 to 6 mCi) was injected after coronary artery occlusion but before reflow. Scintigraphic perfused LV mass was calculated from the total voxels demonstrating Tc-MIBI uptake x voxel volume (cm3) x specific gravity of myocardium (1.05 gm/cm3). After being imaged the animals were killed, the left ventricle was weighed, and the risk area was determined by dual perfusion with phthalocyanine blue dye and triphenyltetrazolium chloride (TTC). Perfused LV mass was defined as total LV mass minus the risk area mass. There was good correlation between scintigraphic and morphologic determinations of perfused left ventricular mass in nonischemic hearts (Tc-MIBI left ventricular distribution = 0.84 x left ventricular weight + .20.4, n = 33, r = 0.93, p = 0.0001) and ischemic hearts (Tc-MIBI left ventricular distribution = 0.51 x left ventricular weight + 37.9, n = 15, r = 0.83, p = 0.0001). In animals imaged both before and after reperfusion, scintigraphic determinations of the nonischemic region correlated closely (after-reflow Tc-MIBI distribution = 1.07 x before-reflow Tc-MIBI distribution--8.0, n = 13, r = 0.88, p = 0.0001), indicating that Tc-MIBI does not significantly redistribute into the ischemic zone after reperfusion. After injection of the second dose of Tc-MIBI in acutely reperfused canines, there was good correlation between the distribution mass of Tc-MIBI and the mass of viable myocardium by TTC staining (Tc-MIBI distribution = 0.61 x viable LV mass + 34.2, n = 12, r = 0.77, p = 0.0001). Furthermore, the apparent redistribution of myocardial Tc-MIBI from before and after second injection images correlated with the degree of myocardial salvage by histochemical staining (r = 0.72, p = 0.0082). In conclusion, single-photon emission computed tomography of Tc-MIBI can measure perfused LV mass accurately in both ischemic and nonischemic canine preparations.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗

PubMed1993

Effects of canine myocardial infarction on sympathetic efferent neuronal function: scintigraphic and electrophysiologic correlates.

We studied the effects of nondecentralized left stellate ganglion stimulation on regional epicardial monophasic action potential duration at 50% (APD50) and 90% (APD90) repolarization from 104 sites in 10 surviving dogs with a chronic myocardial infarction model. These effects were correlated with thallium-201 and iodine-123 metiodobenzylguanidine (MIBG) imaging to identify areas of viable but denervated myocardium. Mean infarct size was 5.2% +/- 0.8% total heart weight, and the planimetered areas of denervation were always larger (18% +/- 4% total heart area). During constant ventricular pacing, stellate stimulation tended to shorten the APD90 only in normally innervated areas (364 +/- 5 to 358 +/- 5 msec) and to increase in denervated areas (358 +/- 5 to 362 +/- 5 msec), (p value not significant (NS) for prestellate and poststellate stimulation; p < 0.05 for difference between denervated vs innervated). The APD50 significantly shortened in innervated areas from 287 +/- 5 to 270 +/- 3 msec (p < 0.05) compared with denervated areas (283 +/- 4 to 274 +/- 5 msec, p = NS). We conclude that MIBG imaging demonstration of denervation identifies areas with impaired shortening of the epicardial APD50 in response to stellate stimulation and that nontransmural myocardial infarction produces areas of denervation larger than areas of necrosis.

Action Potentials↗

PubMed1988

The clinical and pathophysiologic implications of pain, ST abnormalities, and scintigraphic changes induced during dipyridamole infusion: their relationships to the peripheral hemodynamic response.

In order to determine their significance during dipyridamole perfusion scintigraphy, symptomatic, ECG, and scintigraphic findings were related to each other, to the hemodynamic response, and to angiographic findings in 73 consecutive patients having coronary angiography within 3 months of scintigraphy. The group having induced "cardiac" pain differed from the group without induced pain only in their higher incidence of induced ischemic ST changes, the "marked" hemodynamic response, and their lower incidence of an "absent" hemodynamic response (all p less than 0.01). Induced ST depression was found only in patients with coronary disease. In this population, dipyridamole-induced pain was a moderately specific marker and induced ST abnormalities a more highly specific marker for coronary disease. However, both were insensitive for coronary disease diagnosis. If induced pain or ST abnormalities in the presence of significant coronary disease were accepted as indicators of ischemia, then scintigraphic abnormalities appeared to be produced by dipyridamole in roughly equal incidence by ischemic and nonischemic mechanisms. Induced ischemia related frequently to an exaggerated hypotensive response with no change in double product, suggesting its cause to be an induced increase in myocardial oxygen demand. Dipyridamole-induced image defects were noted even in the absence of a peripheral hemodynamic response. This indicates that the peripheral response does not always correlate with its central coronary effect and an absent peripheral hemodynamic response does not necessarily invalidate scintigraphic results.

Angina Pectoris↗

PubMed1988

Gallium lung scintigraphy in amiodarone pulmonary toxicity.

We sought to assess the role of gallium-67 lung scintigrams in the evaluation of amiodarone pulmonary toxicity. Images and laboratory studies were evaluated in 54 patients who had chest radiographs and scintigraphic studies during amiodarone treatment of more than one month's duration among 561 patients receiving the medication for refractory arrhythmias. There were 22 patients with pulmonary symptoms and clinical evidence of amiodarone pulmonary toxicity (group 1); 19 patients had other causes for pulmonary symptoms (group 2); and 21 patients were without symptoms or other clinical evidence of pulmonary toxicity (group 3). There was no difference among groups in treatment duration or total amiodarone dose. Symptomatic presentation could not differentiate between group 1 and group 2 patients. However, radiographic findings of isolated pulmonary congestion or a normal radiograph in the presence of symptoms made amiodarone toxicity unlikely, while the appearance of new, dense radiographic infiltrates--often in a nodular distribution--were more frequent among group 1 patients (p less than 0.01). During symptomatic periods, 18 of 22 group 1 patients had abnormal gallium lung uptake, while four revealed more subtle serial changes but there was only one abnormal scintigram among symptomatic group 2 patients. Nonspecific radiographic abnormalities in patients with pulmonary symptoms on amiodarone therapy were rarely attributed to toxicity in the presence of a normal scintigram. One group 3 patient developed scintigraphic abnormalities early during amiodarone treatment, suggesting toxicity in the presence of a normal chest x-ray examination. Comparison of radiographic and scintigraphic studies performed during symptoms with those performed prior to symptom development best indicated the diagnosis, while comparison with later images assessed the efficacy of treatment. Diffusion capacity testing and transbronchial biopsy were sensitive but not specific for the diagnosis of amiodarone toxicity. Gallium image abnormalities parallel the development of amiodarone pulmonary toxicity and aid this diagnosis, especially when the chest radiograph is abnormal and ambiguous. Serial increments in scintigraphic abnormality appear especially helpful for diagnosis in the population at risk.

Adult↗

PubMed1987

Augmented preexcitation assessed by scintigraphic phase analysis during atrial pacing.

We sought to characterize the effect of augmented preexcitation on the phase image pattern associated with scintigraphic acquisition during conduction via accessory arteriovenous connections. For this reason we assessed phase image scintigraphy, acquired in sinus rhythm and during rapid atrial pacing in 12 patients with documented right (five patients) or left (seven patients) lateral accessory pathways. Augmented preexcitation during atrial pacing was documented at electrophysiologic study in all patients during atrial pacing at similar rates. Phase analysis was abnormal in only 8 patients during sinus rhythm but in all 12 patients during atrial pacing. Atrial pacing brought a significant delay in both mean left and right ventricular phase angles, LV phi and RV phi, respectively. With atrial pacing, the site of earliest phase angle, interpreted to indicate the site of earliest excitation, shifted to the site of the accessory pathway. There was increased relative "prematurity" of the mean phase angle of the ipsilateral ventricle and an absolute increase in the difference between mean and earliest left and right ventricular phase angles, delta phi (LV-RV) and delta phi 0 (LV-RV), respectively. In patients with right-sided pathways, delta phi (LV-RV) increased from 9.5 +/- 12.6 degrees to 47.9 +/- 22.8 degrees, whereas delta phi 0 (LV-RV) increased from 28.1 +/- 18.0 degrees to 67.6 +/- 25.0 degrees (both p less than 0.05). Patients with left-sided pathways demonstrated similar changes in which delta phi (LV-RV) decreased from 2.9 +/- 10.8 degrees to -26.5 +/- 9.0 degrees and delta phi 0 (LV-RV) decreased from 3.4 +/- 14.2 degrees to -27.4 +/- 17.9 degrees (both p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1987

Effects of altered coronary perfusion pressure on function and metabolism of normal and cardiomyopathic hamster hearts.

The effects of a sudden decrease in coronary perfusion pressure from 140 to 0 cmH2O for a 10-second interval were analyzed in normal and cardiomyopathic hamster hearts to determine whether cardiomyopathy would affect the relationship between altered coronary perfusion pressure and left ventricular geometry, wall thickness, myocardial hydrodynamics, and hemodynamics. In normal hamsters, an acute reduction in coronary perfusion pressure resulted in a decrease in left ventricular short axis epicardial cross-sectional area, base to apex length, diastolic wall thickness, myocardial water content and developed pressure. In cardiomyopathic hamsters all results induced by lowering the hydrostatic pressure of the perfusing medium were the same except that diastolic wall thickness failed to decline, indicating a decrease in intramyocardial elasticity in dilated cardiomyopathy. In parallel studies, hearts were freeze clamped at end-diastole and high energy phosphates and energy metabolites analyzed. In both normal and cardiomyopathic hamsters no significant changes were observed in ATP, PCr, or Pi levels at 10 s following the decrease in perfusion pressure. However, during the abrupt decrease in coronary perfusion pressure adenosine increased and cAMP decreased in both groups of animals. The erectile effect of altered coronary perfusion pressure is partially attenuated in the cardiomyopathic hamster in which no change in diastolic wall thickness occurs during an abrupt change in the hydrodynamics of the heart.

Animals↗

PubMed1986

Quantitation of regional myocardial function by cine computed tomography: pharmacologic changes in wall thickness.

To determine the capability of high speed computed transmission tomography to quantitate regional wall thickening dynamics over a wide range of physiologic states, left ventricular wall thickening was studied in nine anesthetized mongrel dogs in the control state and during separate infusions of dobutamine (10 micrograms/kg per min) and phenylephrine (25 micrograms/kg per min). After an intravenous bolus of contrast medium the heart was imaged from base to apex with serial transverse images in eight short-axis cine computed tomographic planes. In each dog during each experimental condition, 50 ms scans spanning the cardiac cycle were acquired at each anatomic level. Left ventricular epicardial and endocardial boundaries were identified on end-diastolic and end-systolic images at the equatorial left ventricular planes by an objective threshold contour method validated in a series of experiments performed on ex vivo anatomic specimens. End-diastolic and end-systolic frames were automatically realigned by superposition of epicardial centers of gravity and then rotated using a cross correlation function. The left ventricular wall thickness was measured manually at 16 points around the circumference by two independent observers. For the group of dogs the average percent wall thickening was 40.5 +/- 28.2% and varied among segments from 18 to 70% in the control state. After dobutamine was administered, significant increases in heart rate and cardiac output (p less than or equal to 0.01) were accompanied by an increase in the average wall thickening (73.6 +/- 51.2%; p less than or equal to 0.001) in the left ventricle; the average wall thickening among segments ranged from 46 to 97%. After phenylephrine administration, significant increases in mean blood pressure and cardiac output (p less than or equal to 0.01) were noted along with a significant increase in average left ventricular wall thickening (60.3 +/- 52.5%; p less than or equal to 0.001). Despite an overall increase in the percent wall thickening, no statistically significant changes in segmental contraction pattern between control and drug intervention states were observed. The wall thickness measurements were highly reproducible between the two independent readers (reliability coefficient = 0.99). Cine computed tomography-derived measurements can potentially be used for quantitative assessment of left ventricular wall thickening dynamics of a single heartbeat during acute interventions, such as the administration of drugs.

Animals↗

PubMed1986

Differentiation of reversible and irreversible myocardial injury by MR imaging with and without gadolinium-DTPA.

The current study evaluated the capability of magnetic resonance (MR) imaging to distinguish myocardium subjected to reversible and irreversible ischemic injury. Nine dogs underwent left anterior descending coronary arterial occlusion for 15 minutes (reversible injury) and nine for 1 hour (irreversible injury), followed by reperfusion for 24 hours in both groups. Six dogs from each group received 0.5 mmol/kg of gadolinium-DTPA intravenously; the remaining dogs received no contrast media. In the dogs with irreversible injury but no contrast media, there were prolonged T1 and T2 of the infarcted myocardium and adequate visualization of the infarct. The percentage of contrast between normal and infarcted myocardium was greatest on T2-weighted images. In the group with irreversible injury and contrast media, Gd-DTPA produced significant T1 shortening of injured myocardium, with resultant high signal intensity of the infarct, and significantly enhanced contrast compared with the group that did not receive Gd-DTPA. In the dogs with reversible injury, there were no regional differences in intensity or relaxation times. MR has the capability to distinguish myocardium with irreversible injury from that with reversible injury. The difference of T1 between normal and reperfused infarcted myocardium is increased by Gd-DTPA; thus, contrast between these two is enhanced on MR images.

Animals↗

PubMed1985

Measurement of cardiac output by cine computed tomography.

High-speed computed transmission tomography (cine CT) is a new noninvasive technique that may be useful for the rapid, accurate quantitation of cardiac function. The capability of cine CT to assess cardiac output was examined 10 mongrel dogs as an initial step in validating this method. After the dogs were anesthetized, femoral arterial pressure and pulmonary artery thermodilution catheters were inserted. After intravenous injection of a bolus of contrast medium, cine CT scans were performed in the flow mode, in which 50-ms scans were triggered electrocardiographically at end-diastole at 8 levels during sequential cardiac cycles. Scans and thermodilution measurements of cardiac output were obtained at rest and during altered hemodynamic states induced by separate infusions of dobutamine and phenylephrine. Time-density analysis was performed over the left ventricular cavity and curves were fitted to the CT flow data by gamma-variate analysis. Using the Stewart-Hamilton equation established for indicator dilution techniques, the cardiac output was calculated. The results established a direct linear correlation (r = 0.92) between cine CT cardiac output and thermodilution cardiac output over a wide range of cardiac outputs (1.5 to 6.3 liters/min). This study demonstrates that cine CT can provide a reliable estimate of cardiac output noninvasively using contrast medium as an indicator in dogs.

Cardiac Output↗

PubMed1985

Magnetic resonance imaging in hypertrophic cardiomyopathy.

Gated magnetic resonance imaging (MRI) was performed using a 0.35-Tesla cryogenic system in 14 patients with hypertrophic cardiomyopathy (HC) in order to define the site and extent of abnormal wall thickness. These studies were compared with 2-dimensional (2-D) echocardiograms. Gated magnetic resonance imaging studies in 12 normal volunteers were used for comparison. In normal subjects and in patients with HC, the sharp demarcation of the myocardial wall permitted measurement of wall thickness. The thickness of the septal and posterolateral walls in normal subjects was 10.2 +/- 0.4 mm (+/- standard deviation) and 10.8 +/- 0.5 mm, respectively, whereas septal thickness in all but 1 patient with HC was 15.0 mm or greater. In patients with HC, septal and posterolateral wall thickness were 2.2 +/- 0.8 cm and 1.3 +/- 0.17 cm, respectively, by MRI. The 2-D echocardiographic measurements for septal and posterolateral walls were 2.4 +/- 0.6 cm and 1.4 +/- 0.7 cm, respectively. The severity and distribution of abnormal wall thickness were comparable on 2-D echo and MRI. Gated MRI is an effective and completely noninvasive technique for demonstrating the presence, site and extent of abnormal wall thickness in HC. The large field of view, ability to image directly in multiple planes, and discrete blood-endocardial interfaces are advantages for cardiovascular imaging.

Adult↗

PubMed1985

Interaction of "supplementary" scintigraphic indicators of ischemia and stress electrocardiography in the diagnosis of multivessel coronary disease.

Lung uptake, ventricular cavitary dilation and basal myocardial uptake represent abnormalities that have been associated with myocardial ischemia on stress thallium-201 images, but that are supplementary to the conventional assessment of perfusion distribution. These "supplementary" indicators of ischemia were related to the coronary distribution of perfusion abnormalities, the results of electrocardiographic stress testing and to the findings on coronary angiography in 73 patients. Forty patients had multivessel coronary disease; 19 of these had three vessel disease. Perfusion abnormalities were seen in 39 of these 40 patients but were indicative of multivessel coronary disease in only 28 and of three vessel disease in only 6. However, supplementary indicators were present in 33 of 40 patients with multivessel disease and in 15 of 19 with three vessel disease. Furthermore, they were seen in 16 of 22 patients with multivessel disease in whom conventional perfusion abnormalities underestimated the extent of disease, but in only 4 of 12 patients in whom the extent of disease was overestimated. The presence of either perfusion abnormalities in a multivessel distribution or supplementary indicators identified 38 (95%) of 40 patients with multivessel disease. A markedly positive electrocardiographic treadmill test was a less sensitive indicator of multivessel disease, appearing in only 15 of 40 patients. However, it was present in only 4 of 33 patients without multivessel coronary disease and was more specific for that diagnosis than were supplementary scintigraphic indicators (88 versus 67%, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1985

Assessment of cardiac anatomy using nuclear magnetic resonance imaging.

Nuclear magnetic resonance imaging has emerged in the past few years as a completely noninvasive method for medical imaging of internal organs. Because of the loss of signal intensity by motional nuclei (hydrogen) using most proton imaging techniques, flowing blood within the cardiovascular system generates little or no signal and consequently there is high natural contrast between blood and the walls of blood vessels or cardiac chambers. However, motion during imaging also complicates cardiac imaging because signal is lost from the nuclei in the moving cardiac structures. Consequently electrocardiographic gating of data acquisition is required for nuclear magnetic resonance imaging of the heart. Distinct advantages of nuclear magnetic resonance imaging in relation to other imaging modalities are good contrast between soft tissues and the capability for characterization of specific tissues by estimation of magnetic relaxation times. Early in vitro studies measuring relaxation times of myocardial tissue samples of excised hearts indicate that nuclear magnetic resonance imaging will be capable of discriminating infarcted from normal myocardium. Recent studies using electrocardiographically gated nuclear magnetic resonance imaging of dogs with acute infarction showed the infarct as a region of high intensity on spin-echo images. Initial clinical experience with electrocardiographically gated nuclear magnetic resonance imaging (0.35 tesla) in patients has clearly defined internal cardiac anatomy without the use of contrast media. This technique has demonstrated the consequence of previous myocardial infarction such as regional wall thinning, aneurysm, thrombus and contractile dysfunction, a number of pericardial abnormalities and the morphology of hypertrophic and congestive cardiomyopathies.

Coronary Circulation↗

PubMed1985

The etiology and implications of dense cavitary "photopenia" on myocardial perfusion scintigraphy.

Dense cavitary "photopenia" was observed on 21 of 200 consecutive stress perfusion scintigrams. A prominent finding in many cases, it sometimes occupied only a portion of the region overlying the ventricular cavity, was often seen in some projections and not others, and was frequently adjacent to myocardial perfusion defects. To distinguish an etiology among reduced cavitary radioactivity, relatively increased background radioactivity, or reduced radioactivity in overlying myocardium, quantitative analysis of cavitary, lung and myocardial radioactivity was performed in patients with dense cavitary "photopenia," with and without lung uptake, and compared with results from studies showing increased lung uptake without cavitary photopenia and with normal studies. The results showed that dense cavitary photopenia was related to reduced radioactivity in overlying myocardium. Correlative imaging studies performed with echocardiography and contrast ventriculography confirmed this relationship to myocardial scar in 15 of 21 patients in whom associated akinesis or dyskinesis was seen. Hence, dense cavitary photopenia on stress perfusion scintigraphy is due to a dense myocardial perfusion abnormality, and is often indicative of related scar and an associated severe contraction abnormality.

Adult↗

PubMed1985

Effects of intravenous administration of a new nonionic dimeric contrast medium on the coronary circulation. Comparison with monomeric ionic and nonionic media.

Contrast media injected into the circulation produce a variety of cardiovascular effects. Agents with low osmolality and low concentrations of cations cause considerably less hemodynamic effects. This study compared the effects of a nonionic dimer, iotrol, which has an osmolality (340 mosm/kg) close to that of serum (290 mosm/kg), with a standard ionic monomer, meglumine diatrizoate, and a nonionic monomer, iosimide. The effects of intravenous bolus injection of these three contrast agents on coronary and systemic hemodynamics were studied in eight anesthetized dogs. The influence of the contrast media on subendocardial and subepicardial perfusion was assessed by injecting radioactive microspheres into the left atrium 30 seconds after injection of the media. Alterations in coronary hemodynamics occurred with both iosimide and meglumine diatrizoate. Iotrol produced minimal changes in coronary hemodynamics. Thus, iotrol is the least perturbing contrast indicator and seems the best for use in quantitative digital subtraction and dynamic computed tomography studies designed to measure myocardial perfusion.

Animals↗