Relation between regional distribution of thallium-201 and myocardial blood flow in normal,acutely ischemic,and infarcted myocardium

Myocardial localization of thallium-201 was compared with direct measurements of myocardial perfusion in normal, acutely ischemic, and recently infarcted myocardium. Studies were performed in 6 chronically instrumented dogs that were subjected to myocardial infarction by occlusion of the proximal left circumflex coronary artery. Four days after myocardial infarction, thallium-201 and 9 ± 1 μm niobium-95-labelled microspheres were injected simultaneously after acute left anterior descending coronary arterial occlusion; the animals were killed 5 minutes later and the entire left ventricle was sectioned into 1 to 2 g samples. Regression analyses between thallium-201 activity and regional myocardial blood flow using all myocardial samples demonstrated a very close linear relation in each dog; r values were 0.98 or greater, indicating that the initial localization of thallium-201 in acutely ischemic and recently infarcted myocardium as a function of regional blood flow was essentially identical. Consequently, in each dog the regional distribution of thallium-201 closely approximated myocardial perfusion over a wide range of blood flow and potentially different local metabolic conditions that may be encountered in the clinical use of the isotope.     

Long-term ambulatory therapy with prazosin versus placebo for chronic heart failure: relation between clinical response and left ventricular function at rest and during exercise

The effects of oral prazosin (PZ), 15 to 20 mg/day, on symptoms, exercise performance and left ventricular (LV) function were assessed in a 6-month, double-blind, placebo-controlled study of patients in New York Heart Association functional class III. Ejection fraction (EF) was measured at rest and during upright bicycle exercise by equilibrium radionuclide angiography; end-diastolic volume, stroke volume and cardiac output were derived from corresponding count measurements. Although there was no statistically significant difference between clinical responses in the prazosin and placebo groups, qualitative differences suggested a clinical response to prazosin. Of the 9 patients who received PZ, 5 improved to functional class II and 2 became asymptomatic; the 2 nonresponders deteriorated to functional class IV when PZ was stopped. Four of 9 patients who received placebo improved to functional class II and 2 deteriorated to class IV. Exercise time tended to increase in the prazosin group (from 541 ± 204 to 630 ±100 seconds at 6 months) and decrease in the placebo group (from 539 ± 141 to 435 ±148 seconds at 6 months), but neither change was significant. Prazosin effected a sustained decrease in mean blood pressure of approximately 10 mm Hg at rest, and a quantitatively similar but insignificant decrease during exercise. Radionuclide EF increased and LV end-diastolic counts decreased significantly at rest and during exercise in the prazosin group, but not in the placebo group. Because changes in EF and end-diastolic counts were similar, stroke counts and count output were unchanged. Thus, long-term oral PZ therapy caused sustained changes in blood pressure and LV function in most patients in functional class III, but these changes were not uniformly translated into clinical improvement or increased exercise tolerance. Prazosin does not appear to increase cardiac output during exercise in patients with heart failure.     

Comparison of multigated radionuclide angiography with ultrasonic sonomicrometry over a wide range of ventricular function in the conscious dog

This study compared the noninvasive assessment of left ventricular function with radionuclide angiography with that obtained with ultrasonic sonomicrometry. Left ventricular ejection fraction and rate of ventricular ejection (dV/dt) were measured with both techniques over a wide range of ventricular function. Six dogs were prepared with epicardlal crystals across the major and minor axes of the left ventricle, paired transmural wall thickness crystals and a left ventricular catheter. The animals were studied while awake after they had recovered from operation. Left ventricular volume was calculated from the ultrasonic sonomicrometric dimension measurements and the equation for a prolate ellipsoid; dV/dt was calculated from the stroke volume and ejection time. Radionuclide angiograms were performed using technetium-99m-labeled red blood cells and an Anger camera with a converging collimator interfaced to a computer programmed for multigated acquisition.A wide range of ventricular function was produced with sequential infusion of isoproterenol, propranolol, phenylepnrine and sodium thiamylal. Ejection fraction and dV/dt were measured simultaneously during each intervention using the time-activity curves of the multigated radionuclide anglogram and ultrasonic sonomicrometric dimensions. Regression analyses demonstrated a close correlation between the simultaneous measurements of ejection fraction (r values ranged from 0.95 to 0.99) and dV/dt (r values ranged from 0.87 to 0.99). these data indicate that noninvasive multigated radionuclide angiography accurately assesses changes in ejection fraction and dV/dt over a wide range of ventricular function.     

Importance of complete revascularization in performance of the coronary bypass operation

Cardiac Data Bank records of 1,238 patients with triple-vessel disease (greater than or equal to 50% diameter reduction) who had undergone coronary bypass surgery were reviewed and divided into 2 groups depending on whether complete (n = 773) or incomplete (n = 465) revascularization had been accomplished. Patients with complete revascularization had a higher incidence of a normal preoperative electrocardiogram than did patients with incomplete revascularization (23 versus 14%, respectively, p less than 0.0001). The ejection fraction for both completely and incompletely revascularized patients was good (m = 0.60 and 0.57, respectively). The mean number of grafts per patient for the 2 groups was 3.8 and 2.6 (p less than 0.0001). There was no significant difference between the 2 groups with regard to postoperative inotropic requirements (8 and 7%), ventricular arrhythmias (1.8 and less than 1%), necessity for intraaortic balloon pumping (1.6 and 1.5%, hospital mortality (1.2 and 2.8%), or myocardial infarction (4.3 and 4.8%). Survival at 5 years was significantly greater (p less than 0.001) in patients with complete (88.5%) than in those with incomplete revascularization (83.5%). Reemployment occurred more often in patients with complete (52%) than in those with incomplete revascularization (40%) (p less than 0.001), and more patients were free of angina after complete (70%) than after incomplete revascularization (58%) (p less than 0.0005). Long-term survival appeared to be mediated primarily through improved revascularization rather than through differences in left ventricular function.     

Anatomic and prognostic implications of an early positive treadmill exercise test

Eighty men (group A) with clinical coronary artery disease underwent coronary angiography regardless of symptoms and previous therapy because they had a positive treadmill exercise test in stage I or II of the Bruce protocol. Thirty-four other men (group B) who also had an early positive treadmill test underwent coronary angiography because they had disabling angina pectoris despite medical therapy. We found left main coronary artery stenosis of 50% or greater of the vessel diameter in 28% of group A and 35% of group B (p >0.3). In contrast, only 10% of 93 other catheterized patients who had treadmill tests that were not early positive had left main coronary disease (p < 0.001). Fifty-four patients from group A who did not have left main stenosis of 50% or greater were treated medically. In this subgroup, 85% had 2 or 3 major coronary vessels with 75% or greater stenosis. These patients had a 36 month survival rate of 89.2%.We conclude that an early positive treadmill test identifies patients who have an increased likelihood of having left main coronary stenosis, even if they are minimally symptomatic. To identify left main coronary stenosis, catheterization may be justified in patients whose angina pectoris has been mild or not intensively treated when they have an early positive treadmill response. After left main coronary stenosis has been excluded, these patients may be treated medically with a low mortality.     

Assessment of left ventricular function by resting and exercise radionuclide angiocardiography following acute myocardial infarcton

Left ventricular function was evaluated by first-pass radionuclide angiocardiography in 42 patients at 3 and 8 weeks following acute myocardial infarction. Left ventricular ejection fraction, diastolic volume, and wall motion were measured at rest and submaximal exercise at 3 weeks and at rest, submaximal and maximal exercise at 8 weeks. The mean ejection fraction, end-diastolic volume, and wall motion index did not change between 3 and 8 weeks in any group either at rest or during submaximal exercise. Ventricular function was decreased at rest in patients with previous and anterior myocardial infarction, but not in patients with inferior and subendocardial myocardial infarctions. During maximal exercise at 8 weeks, nine patients (21%) had ST segment depression, whereas 25 patients (60%) had a decrease in ejection fraction or a deterioration in wall motion. These abnormalities of ventricular function during exercise occurred equally among the infarct groups. Radionuclide angiography in patients with recent myocardial infarction demonstrated highly variable ventricular function at rest and/or during exercise in each infarct subgroup.     

Effect of propafenone on left ventricular ejection fraction

The effects of orally administered propafenone on ejection fraction (EF) determined by radionuclide angiography were studied in 2 groups of patients receiving different dosing regimens. Fourteen group A patients had no clinical evidence of left ventricular (LV) dysfunction and were not receiving digoxin therapy. In this group a mean daily dosage of 879 mg resulted in a decrease in resting LVEF from 52 +/- 9% to 48 +/- 11% (p less than 0.05). Eight group B patients had clinical radionuclide evidence of LV dysfunction and were receiving digoxin therapy. In this group, a daily dosage of propafenone of 600 mg/day resulted in no significant change in LVEF. No clinically significant effects on cardiac compensation were evident in either group. These data suggest a negative inotropic effect that is either related to propafenone dosage or at least partially attenuated by digoxin therapy. Further studies are necessary to define precisely the effects of propafenone on LV function.     

Right ventricular ejection fraction measurement: Contrast ventriculography versus gated blood pool and gated first-pass radionuclide methods

Radionuclide methods of measuring the right ventricular (RV) ejection fraction (EF) provide noninvaslve means of evaluating right-sided cardiac function at rest and exercise. This study compared 2 radionuclide methods with a cast-validated contrast anglographic method of RVEF analysis in 21 consecutive patients who underwent RV contrast ventriculography and gated equilibrium blood pool radionuclide ventriculography. Eleven subjects had gated first-pass radionuclide studies that were technically adequate for EF analysis. RVEF was calculated by different operators for the contrast and radionuclide methods. The close correlation of the contrast angiographic method with both equilibrium blood pool and first-pass radionuclide methods supports the use of the radionuclide techniques.     

Detection of left ventricular thrombi with radionuclide angiography

Apparent filling defects compatible with left ventricular thrombus are occasionally noted in equilibrium radionuclide angiocardlograms. To define the usefulness of the radionuclide angiogram in detecting left ventricular thrombus, the anterior and left anterior oblique radionuclide angiograms of 39 patients with proved presence or absence of thrombus were blindly interpreted. The presence of thrombus was proved at autopsy in 5 patients, at cardiac operation in 2, or on indium-111 platelet imaging in 6; the absence of thrombus was proved at autopsy in 24 or at cardiac operation in 2. Overall, 13 radionuclide angiograms were interpreted as posltive (n = 10) or equivocally positive (n = 3) for thrombus, and 26 studies were judged negative. The sensitivity of a positive or equivocally positive radionuclide angiogram for detection of thrombus was 77 percent (10 of 13 patients), the specificity 88 percent (23 of 26 patients), the positive predictive value 77 percent, the negative predictlve value 88 percent. If the three equivocal studies are instead considered negative for thrombus, the sensitivity was 62 percent, the specificity 92 percent, the positive predictive value 80 percent and the negative predictive value 93 percent. All thrombi were visualized in the anterior view in an area of akinetic or dyskinetic wall motion. A small group of 13 patients (8 with thrombus, 5 without) underwent two dimenslonal echocardiography, which was 100 percent sensitive and specific. The finding of a discrete filling defect or squared or cutoff ventricular apex in an area of abnormal wall motion in the anterior view of the radionuclide angiogram should suggest the diagnosis of ventricular thrombus, which may be confirmed by other noninvasive studies.     

Effects of age on radionuclide angiographic detection and quantitation of left-to-right shunts

The usefulness of quantitative radionuclide angiography (RNA) in detecting left-to-right shunts and estimating shunt size in young children was assessed. The total population of 88 patients was divided into 2 groups: 23 patients 2 years of age and younger (mean 0.8 +/- 0.6 [+/- standard deviation] ) and 65 patients older than 2 years (mean 15 +/- 15 years). The accuracy of 2 different RNA shunt estimation techniques, the gamma variate and the Stewart-Hamilton approach, were compared with the estimations obtained at cardiac catheterization using Fick (88 patients) and indocyanine green dye-dilution techniques (20 patients). Automated data processing algorithms were used to determine the RNA estimations, thereby avoiding the effects of operator judgment and subjectivity on shunt estimation. Of the 88 patients, 16 had no shunt by Fick data (that is, estimation less than 20%) but had a left-to-right shunt demonstrated by cardiac catheterization cineangiocardiography. Nine of these patients had no shunt by RNA (that is, estimation less than 20%). For patients 2 years of age and younger, linear regression analysis of the Fick and gamma variate data provided a slope of 0.63 and a correlation coefficient of 0.82; analysis of the Fick and Stewart-Hamilton data provided a slope of 0.59 and a correlation coefficient of 0.79. For patients older than 2 years, analysis of the Fick and gamma variate data provided a slope of 0.63 and a correlation coefficient of 0.79; analysis of the Fick and Stewart-Hamilton data provided a slope of 0.64 and a correlation coefficient of 0.76.(ABSTRACT TRUNCATED AT 250 WORDS)     

Relation between QRS changes and left ventricular function after coronary artery bypass grafting

Preoperative and serial postoperative electrocar-diograms (ECGs) were reviewed in 104 patients undergoing rest and exercise radionuclide angiocardiography before and 1 to 12 months after coronary artery bypass grafting (CABG). Five patient groups were defined by ECG findings before and after CABG: Group I—normal ECG before and no ECG change after CABG; Group II—prior myocardial infarction by ECG before but no QRS change after CABG; Group III—all patients with a minor QRS change (< 0.04-second Q wave, loss of R-wave amplitude) after CABG; Group IV—all patients with a major QRS change (≥ 0.04-second Q wave) after CABG; Group V—all patients without new Q waves or loss of R-wave amplitude but with a major QRS change (conduction disturbance) after CABG. Mean resting ejection fraction changed little after CABG in all groups, although the 0.03 increase in Group I was significant (p < 0.05). Group IV had the largest decrease in resting ejection fraction after CABG (0.04), but this was not statistically significant. Mean exercise ejection fraction increased significantly (p < 0.0001) in Groups I, II and III but not in Groups IV and V. QRS changes do not consistently reflect impairment of left ventricular (LV) function after CABG.     

Effects of atrial pacing on global and regional left ventricular function in coronary heart disease assessed by digital intravenous ventriculography

Digital i.v. ventriculography in conjunction with rapid atrial pacing was used to assess the effects of ischemic stress on global and regional function in 22 patients referred for cardiac catheterization (5 had normal coronary arteries and 17 had greater than 70% diameter reduction of at least 1 major coronary artery). End-diastolic, end-systolic and stroke volume indexes and the ejection fraction were determined by an area-length technique from the mask mode images before and after pacing. In addition, segmental responses were quantitated using a radial shortening method. Subjects with normal coronary arteries showed no overall change in the postpacing volume or ejection fraction indexes. Coronary patients showed no overall change in postpacing end-diastolic volume (86 +/- 25 ml/m2 at control vs 90 +/- 31 ml/m2 after pacing, difference not significant), but there was a significant increase in end-systolic volume (25 +/- 15 ml/m2 at control vs 32 +/- 18 ml/m2 after pacing, p less than 0.005) and a decrease in ejection fraction (72 +/- 11% at rest vs 64 +/- 18% after pacing, p less than 0.025). Furthermore, quantitative deterioration in wall motion was seen in 14 of 17 coronary patients (82%) and in none of the normal patients. Analysis of segmental wall motion was the most sensitive diagnostic variable. A combination of atrial pacing stress testing and digital i.v. ventriculography is useful in detecting functionally significant coronary disease through quantitation of global and regional dysfunction which does not require arterial cannulation.     

Relation of right ventricular ejection fraction to exercise capacity in chronic left ventricular failure

Although the left ventricle is traditionally viewed as the heart's main pumping chamber, no correlation has been shown between left ventricular (LV) ejection fraction (EF) at rest and exercise capacity in patients with chronic LV failure. Because vasodilators with venodilating activity increase exercise capacity more than predominant arterial dilators in patients with LV failure, right ventricular (RV) function may relate to exercise capacity in these patients. In 25 patients with chronic LV failure, caused by coronary artery disease in 12 patients and idiopathic dilated cardiomyopathy in 13 patients, RVEF and LVEF at rest were measured by radionuclide angiography. Maximal upright bicycle exercise testing was also performed to determine maximal oxygen consumption, which averaged only 13 ± 4 ml/min/kg. The LVEF at rest was 26 ± 10% and did not correlate with maximal oxygen consumption (r = 0.08). However, the RVEF was 41 ± 12% and correlated with maximal oxygen consumption (r = 0.70, p < 0.001) in the same patients. The correlation was stronger (r = 0.88) in patients with coronary artery disease than in those with idiopathic dilated cardiomyopathy (r = 0.60). Thus, RVEF at rest is more predictive of exercise capacity than LVEF in the same patients with chronic LV failure. These results are consistent with the clinical observation that only venodilating agents increase exercise capacity of patients with chronic LV failure.     

Spatial R wave amplitude changes during exercise: relation with left ventricular ischemia and function

Thirty patients who exhibited increased and 65 patients decreased spatial R wave amplitude during exercise testing were compared for left ventricular function and ischemic variables. Spatial R wave amplitude was derived from the three-dimensional Frank X, Y, Z leads using computerized methods. All patients had stable coronary artery disease and they were classified into two groups: one that attained a higher (n = 48) and one a lower (n = 47) median value of maximal heart rate during exercise (161 beats/min). Within these two groups, patients with increasing or decreasing spatial R wave amplitude during exercise were analyzed for differences in oxygen consumption, exercise-induced changes in spatial R wave amplitude, ST segment depression laterally (ST60, lead X), ST displacement spatially, left ventricular ejection fraction at rest, change in left ventricular ejection fraction with exercise and thallium-201 ischemia during exercise. Significant differences were demonstrated only in exercise-induced spatial R wave amplitude changes (p less than 0.0001). There was no significant correlation between exercise-induced change in heart rate and change in spatial R wave amplitude in either the group with increasing or the group with decreasing spatial R wave amplitude. It is concluded that changes in spatial R wave amplitude during exercise are not related to ischemic electrocardiographic or thallium-201 imaging changes or to left ventricular ejection fraction determined at rest or during exercise.     

Value of the QRS complex in assessing left ventricular ejection fraction

The relation between electrocardiographic findings and the angiographic left ventricular ejection fraction and the augmented ejection fraction after a premature ventricular contraction was investigated in 73 patients with documented chronic coronary artery disease. The patients were separated into four groups according to the presence or absence of abnormal Q waves. Twenty-four patients had diaphragmatic myocardial infarction, 21 had anterior myocardial infarction, 15 had both and 13 had no myocardial infarction. There were no statistically significant differences in cardiac index, left ventricular end-diastolic pressure or number of coronary vessels showing critical narrowing in the four groups. The sum of R waves (in mv) in leads aVL, aVF and V₁ to V₆ (ΣR) was correlated with the ejection fraction (EF) and the augmented ejection fraction (EFa). EF in percent = 6.6 ΣR mv + 9.4 (no. = 73, r = 0.61); and EFa in percent = 8.6 ΣR mv + 11.0 (no. = 73, r = 0.77). Among patients with ΣR of less than 4.0 mv, augmented ejection fraction was less than 0.45 in 73 percent; among patients with ΣR of 4.0 mv or more the augmented ejection fraction was greater than 0.45 in 93 percent (P < 0.001). Thus, the ΣR, calculated from six precordial and two augmented leads in patients with chronic coronary artery disease, correlated with both ejection fraction and augmented ejection fraction. The electrocardiogram in patients with coronary artery disease may prove useful as a simple, readily available and noninvasive guide in the assessment of left ventricular function in patients with coronary artery disease.     

Failure of antihypertensive therapy with diuretic,beta-blocking and calcium channel-blocking drugs to consistently reverse left ventricular diastolic filling abnormalities

The present protocol was designed to determine whether antihypertensive therapy with hydrochlorothiazide, propranolol or diltiazem, 3 agents with different mechanisms of action and potentially different effects on myocardial function, reverses left ventricular filling abnormalities. Twelve patients with essential hypertension and no evidence of associated cardiovascular disease, either clinically or with noninvasive testing, were evaluated while taking no medication and after 2 months of treatment with these agents. All 3 drugs produced equivalent control of blood pressure (BP), reducing sitting systolic BP by a mean of 20 to 24 mm Hg and diastolic BP by 14 to 16 mm Hg. LV ejection fraction and end-diastolic volume were normal in all but 1 subject (who was excluded from the analyses of LV diastolic filling) and were not altered by drug therapy. The peak LV filling rate and the first-third filling fraction were reduced in the patients with hypertension, but neither of these indexes nor the time to peak filling rate were significantly improved for the group as a whole by any of these medications. Nine of 10 patients whose BP was controlled by diltiazem had increases in their first-third filling fraction, but this change did not reach statistical significance. Our findings suggest that abnormalities of LV diastolic filling are not consistently affected by short-term therapy in patients with chronic, previously treated systemic hypertension.