Restoration of regional wall motion by nitroglycerin therapy in patients with left ventricular asynergy

Redistribution of myocardial blood flow with topical nitroglycerin in patients with coronary artery disease

BACKGROUND

Unlike nonselective coronary vasodilators, nitroglycerin (GTN) is said to exert its primary vasodilatory effect on epicardial conductance vessels. Thus, in experimental models of coronary occlusion GTN appears to preferentially direct blood flow to poststenotic zones of ischemia. This phenomenon has, to date, not been tested in humans. Using positron emission tomography we examined the effect of transdermal GTN on global and regional myocardial perfusion in patients with angiographically proven coronary artery disease.

METHODS AND RESULTS

Myocardial perfusion with [13N]ammonia was estimated from dynamic time-activity curves at baseline and 3 hours following application of either a 0.4 mg/h GTN skin patch (n = 10) or a placebo patch (n = 10) in a double-blind parallel design. From resliced cross-sectional images, regional flow, expressed as [13N]ammonia retention, was estimated from 216 myocardial sectors. Ischemia was defined as a significant reduction (> 2 SDs from average counts/pixel in maximally perfused zones) in [13N]ammonia retention within 10 contiguous myocardial sectors coupled with an increase or no change in counts derived from [18F]fluorodeoxyglucose. There was no change in global myocardial blood flow as expressed by [13N]ammonia retention following either placebo (0.61 +/- 0.14 to 0.62 +/- 0.12 min-1) or GTN (0.75 +/- 0.22 to 0.74 +/- 0.19 min-1). Conversely, there was a significant increase in the proportion of blood flow to the ischemic zones with GTN (73.9 +/- 12.6% to 94.9 +/- 17.8%; P < .05). No change in the distribution of blood flow to either ischemic or nonischemic zones was observed with placebo. A slight but insignificant decrease in [13N]ammonia retention in nonischemic zones was observed with GTN (1.01 +/- 0.31 to 0.93 +/- 0.26 min-1).

CONCLUSIONS

This study suggests that under resting conditions topical GTN alters myocardial perfusion by preferentially increasing flow to areas of reduced perfusion with little or no change in global myocardial perfusion in patients whose angina is responsive to GTN.

Acute hemodynamic effects of propranolol, glycerylnitrate, and exercise in coronary patients with left ventricular dysfunction

Some adverse effects of beta-blockers in heart failure are counteracted by glycerylnitrate. However, the hemodynamics in this condition after giving both drugs are not well known. We examined the drug combination in exercising coronary patients with left ventricular dysfunction. Elevated left ventricular end-diastolic pressure was a measure of dysfunction. A right-heart catheterization with three successive exercise stress tests was done in 40 patients. At repeated exercise without drugs a "warming up" phenomenon was observed, consisting of small but statistically significant reductions in pulmonary capillary wedge pressure, and heart rate. At exercise propranolol reduced heart rate, cardiac output, systemic blood pressure, left ventricular work, and increased arteriovenous oxygen difference. Glycerylnitrate reduced pulmonary capillary wedge pressure at exercise, but, contrary to the findings at rest, it did not increase heart rate or reduce cardiac output. The drug combination resulted in hemodynamics that were similar to those after propranolol alone, except for a lower pulmonary capillary wedge pressure. The drug combination allowed the patients to exercise with the benefits of the beta-blocker, but at a lower ventricular filling pressure. Thus, the potential hazard of giving beta-blockers to patients with left ventricular dysfunction may be reduced by adding glycerylnitrate.

Effect of glyceryl trinitrate on echocardiographic left ventricular dimensions during exercise in the upright position

Changes in left ventricular size may be of importance in the development of angina and in its amelioration by glyceryl trinitrate, but left ventricular dimensions have not been measured during exercise in the upright position, the circumstance in which angina most often occurs. To assess changes in left ventricular end-systolic and end-diastolic dimensions, echocardiograms were obtained from 5 normal subjects and 6 patients with angina during rest and exercise upright, both before and after glyceryl trinitrate. The end-systolic dimension was considered an index of regional performance rather than an estimate of overall left ventricular behaviour. During exercise the end-diastolic dimension rose both in the normal subjects and in the patients. The end-systolic dimension fell progressively with exercise in the normal subjects but changed inconsistently in the patients. Glyceryl trinitrate lowered the end-diastolic dimension during exercise below comparable pretreatment values in both groups; the glyceryl trinitrate-induced decrease in end-diastolic dimension in the patients diminished at higher exercise levels. In all normal subjects and in 4 of the 6 patients with normal systolic shortening (= end-diastolic--end-systolic dimension) glyceryl trinitrate caused relatively small changes in the end-systolic dimension and systolic shortening on exercise. In contrast, in the 2 patients with hypokinetic ventricles glyceryl trinitrate conspicuously decreased the end-systolic dimension and increased systolic shortening. Thus, during exercise, in the normal subjects and in the patients with normally functioning left ventricles on echocardiography, glyceryl trinitrate caused a modest fall in the end-diastolic dimension and little change in the end-systolic dimension, but in patients with ventricular hypokinesia it greatly improved regional contractile performance. Alleviation of ischaemic hypokinesia during exercise may be an important part of the benefit of glyceryl trinitrate.

Improvement of myocardial perfusion and left ventricular function after coronary artery bypass grafting in patients with unstable angina

Changes in myocardial perfusion and left ventricular function were evaluated pre- and post-operatively (3--6 months) in 14 patients with unstable angina who underwent coronary artery bypass surgery. Perfusion was studied with intracoronary and intragraft injections of radiolabeled macroaggregated albumin particles. Of 20 abnormal perfusion areas identified preoperatively, 13 demonstrated improved perfusion post-operatively. Segmental analysis of the left ventriculogram demonstrated improved wall motion in 29 abnormally contracting segments; 18 normalized. Areas which showed improvement of left ventricular perfusion were invariably associated with improvement of left ventricular wall motion. Five patients showed improvement in perfusion and contraction in areas of apparent old myocardial infarction. Thirteen of the 14 patients had significantly less angina whether or not there was evidence of improved perfusion. However, only those patients who demonstrated improved perfusion had a significant improvement in their treadmill exercise tolerance postoperatively. Thus, patients with unstable angina have perfusion defects which may be reversed as a result of saphenous vein graft surgery. Reversal of these perfusion abnormalities results in improved left ventricular performance and better exercise tolerance postoperatively.

Noninvasive assessment of cardiac function and ventricular dyssynergy by precordial Q wave mapping in anterior myocardial infarction

To determine whether multiple lead precordial electrocardiographic recordings offer an improved index for noninvasive estimation of left ventricular hemodynamic function and segmental dyssynergy, precordial mapping was performed in patients with anterior myocardial infarction, and the number of pathologic Q waves (greater than or equal to 0.04 sec) was counted (Q-Index). Left ventricular function was determined by cardiac catheterization and angiography and correlated with the Q-Index. The Q-Index correlated well with dyssynergy extent (r = 0.84) and inversely with ejection fraction (r= -0.87), stroke work index (r = -0.79) and cardiac index (r = =0.66). Three patient groups were defined by Q-Index; group I, 0.04 sec Q complexes less than 15; group II, 15-25; group III, 26-35. Q-Index related closely to functional classification and survival (mean follow-up 12.2 months): group I, 91%; group II, 81%; group III, 40%. Thus 35-lead precordial Q wave mapping with determination of total number of pathologic Q waves permits practical, atraumatic assessment of hemodynamic and functional status and allows prediction of survival in acute and chronic anterior myocardial infarction.

Effects of nitroglycerine ointment on the apexcardiogram and systolic time intervals

Ten patients with angina pectoris and a previous myocardial infarction were administered nitroglycerine (NTG) ointment, sublingual NTG, and a placebo ointment in a double-blind study. Left ventricular function was monitored noninvasively over 3 hours. Two patients showed no response to any of the NTG preparations and were excluded from the results. Left ventricular function improved in all remaining patients after both the sublingual NTG and the NTG ointment, but not the placebo ointment. This improvement was evidenced by a redution in a wave amplitude and duration of the apexcardiogram (ACG). At the same time the isovolumic relaxation time increased significantly and indicated a reduction in left atrial pressure. Also, a simultaneous improvement in the slope of the systolic wave indicated improved wall motion. The ΔLVET decreased, presumably because of a decrease in venous return due to peripheral pooling. None of these parameters changed significantly during the con trol period or after application of the placebo ointment.

The onset of the effect after sublingual NTG was 3-5 minutes with a duration of 15-30 minutes. The NTG ointment had its onset of action at 20-30 minutes, a peak effect at 90 minutes, and a still significant effect at 3 hours. These findings clearly demonstrate the improvement in left ven tricular function that occurs in patients with ischemic heart disease in the absence of chest pain, and suggests that continual usage would be benefi cial even in patients with infrequent angina.

Effects of nitroglycerin, postextrasystolic potentiation, and pacing-induced ischaemia on wall motion in patients with ischaemic heart disease

The influence of nitroglycerin, postextrasystolic potentiation, and rapid ventricular pacing on total and regional ventricular function was studied in 32 patients with normal ventricular function and in 44 patients with left ventricular asynergy caused by obstructive coronary artery disease. Total ventricular function was assessed by ventriculography and regional ventricular function was analysed by use of 7 hemiaxes. Nitroglycerin increased ejection fraction and decreased left ventricular systolic and end-diastolic pressures in the normally functioning ventricles; apical wall motion increased, while basal wall motion remained unchanged after nitroglycerin in these ventricles. Pressures fell significantly in ventricles with asynergy after nitroglycerin; ejection fraction decreased while wall motion in asynergic areas was inconsistently influenced. Postextrasystolic potentiation augmented ejection fraction by a powerful and homogeneous increase of wall motion in normally functioning ventricles. Asynergic areas and normal areas in diseased ventricles showed identical augmentation of wall motion after a premature beat. Rapid venticular pacing produced a significant increase in end-diastolic pressure and a fall in ejection fraction in patients with obstructive coronary artery disease. Wall motion in normal areas perfused by arteries with critical stenoses was dramatically depressed after pacing, while asynergic areas and normal areas perfused by normal arteries remained unchanged. The results show that normal contractile behaviour can be detected by postextrasystolic potentiation in asynergic areas, suggesting that some normally perfused muscle exists in these areas. Pacing stress does not further deteriorate function in asynergic areas, which suggests the presence of viable and well perfused muscle (within scar tissue) whose function may not profit from revascularization. Pacing-induced asynergy identifies the functional significance of coronary stenoses and suggests that bypass surgery might be beneficial.

Particulate myocardial perfusion scintigraphy: its clinical usefulness in evaluation of coronary artery disease

The determination of myocardial viability is a crucial parameter in the evaluation of a patient with coronary artery disease. Particulate myocardial perfusion scintigraphy (PMPS) is one of several methods available for this determination. A brief comparison between PMPS and two other commonly used methods is described in this review. The technique and analysis are described and applied to 194 patients with 366 surgically bypassed regions. The patients are analyzed for postoperative regional wall function and for total ventricular function as expressed by ejection fraction. PMPS is a highly accurate and unique study for clinically predicting myocardial viability.

Nitroglycerin and ventricular performance. Differential effect in the presence of reversible and irreversible asynergy

The effect of nitroglycerin administration on left venticular performance relative to its ability to improve contraction of asynergic zones was examined in 66 patients with coronary artery disease, divided into those whose asynergic zones responded following nitroglycerin administration and those in whom no response was observed. In the responsive group with asynergy of more than one segment, the ejection fraction improved (P less than 0.001), while in the unresponsive group, it decreased (P less than 0.05). Similarly, in patients with one-segment asynergy, the responsive group exhibited a significant increase in ejection fraction P less than 0.001), while the unresponsive group showed no change. The stroke volume index remained unchanged in the responsive group with asynergy of more than one segment, while it decreased significantly (P less than 0.05) in the unresponsive patients. Left ventricular pressures and volumes changed to a similar degree after nitroglycerin administration in all of the patients, regardless of the responsiveness of asynergic zones. It is concluded that nitroglycerin administration results in a differential effect on total left ventricular performance depending on the responsiveness of asynergic zones.

Radionuclide assessment of nitroglycerin influence on abnormal left ventricular segmental contraction in patients with coronary heart disease

Noninvasive gated cardiac blood pool imaging with technetium-99m autologous erythrocytes was employed to differentiate reversible verus irreversible abnormal ventricular segmental contraction by regional wall and pump responses to sublingual nitroglycerin in 25 patients with chronic coronary heart disease. In 12 patients without ECG infarctions compared to 13 with infarctions, radioisotopic images demonstrated significantly greater percent decreases in end-systolic volumes (33.8 +/- 6.7 SEM vs 187 +/- 4.4; P less than 0.05) without differences in percent reductions in end-diastolicvolumes (13.7 +/- 3.9 vs 11.6 +/- 6.1; NS) and thereby significantly greater percent increases in ejection fractions (9.3 +/- 1.6 vs 4.1 +/- 2.0; P less than 0.05). In the 22 patients with regional dyssynergy, improvement in disordered pattern and extent of localized dyssynergy following antianginal action of nitroglycerin was related to ECG absence of prior infarction. These obsevations demonstrate the clinical accuracy of atraumatic scintigraphy in the detection of reversible localized dyssynergy due to myocardial ischemia in coronary heart disease.

Assessment of ventricular function in coronary artery disease using nitroglycerin and computerized analysis of left ventriculograms

The ability to predict if abnormalities in regional wall motion are reversible would assist in selecting patients for aortocoronary bypass operation. This study shows that asynergic areas of the ventricle may be reversed by nitroglycerin. Thirty-four asynergic areas in 30 patients with coronary artery disease were studied before and after administration of nitroglycerin. Nineteen patients with previous infarction, diagnostic Q waves in their electrocardiogram, and akinetic areas in the left ventricle had no change in their akinetic areas after nitroglycerin administration. Nine of these patients did show increased motion in other hypokinetic areas of the myocardium. Five of 11 patients with no evidence of previous infarction showed a dramatic improvement in akinetic areas after nitroglycerin, while of the remaining 6, 5 showed mild improvement. This illustrates that recoverable asynergic areas may be recognized by nitroglycerin.