Hemodynamic effects of nitroglycerin, propranolol, and their combination in coronary heart disease

The effect of pindolol and isosorbide dinitrate and their combination on exercise tolerance and ECG changes in angina pectoris

The effect of placebo, isosorbide dinitrate (ISDN) (5 mg orally), pindolol (1.0 mg i.v.) and the combination of ISDN and pindolol was tested in 12 patients with stable, exercise-induced angina pectoris and normal resting ECG. A graded submaximal exercise test was performed on a bicycle ergometer 30 min after medication. All patients had ST depression during and shortly after exercise. ISDN and pindolol increased exercise tolerance to a similar degree but through different mechanisms. Pindolol decreased heart rate and markedly reduced ST depression in the ECG, while ISDN had no effect on ECG changes. The combination of ISDN and pindolol was superior to either drug alone in increasing exercise tolerance in angina pectoris.

Right ventricular volumes determined by computerized thermodilution in ischaemic heart disease: effect of exercise and nitroglycerin

In 29 patients with stable ischaemic heart disease, right heart catheterization was performed to assess the effect of exercise and nitroglycerin on right ventricular volumes, which were determined by a new computerized thermodilution system. The coefficient of variation for the determination of right ventricular ejection fraction averaged 11.0 +/- 6.2% (mean +/- standard deviation) at rest and 14.6 +/- 8.1% during exercise. End-diastolic volume index increased from 90 (65-127) ml/m2 [median (range)] at rest to 101 (81-130) ml/m2 (P less than or equal to 0.0001) during exercise. Nitroglycerin reduced this parameter at rest to 77 (44-121) ml/m2 (P less than or equal to 0.05), without affecting exercise values. Resting right ventricular ejection fraction (55 [44-64]%) was diminished by both exercise (to 52 [39-62]%, P less than or equal to 0.05) and nitroglycerin (to 53 [40-65]%, P less than or equal to 0.05). Additionally, nitroglycerin reduced the exercise induced decrease of right ventricular ejection fraction from -3 (-20-10)% to -1 (-15-14)% (P less than or equal to 0.01). Nitroglycerin diminished the left-to-right interventricular end-diastolic pressure gradient, which was estimated from the difference between pulmonary capillary wedge pressure and right atrial pressure, at rest from 6 (1-17) mmHg to 5 (2-14) mmHg (P less than or equal to 0.05) and during exercise from 17 (6-31) mmHg to 14 (1-33) mmHg (P less than or equal to 0.001). It is concluded, that both exercise and nitroglycerin cause significant changes in right ventricular volumes.(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of intravenous and oral sotalol

Beta-adrenergic blocking agents may have negative inotropic effects that are particularly worrisome in patients with depressed cardiac function. Their membrane-stabilizing properties may be a contributing factor. Sotalol is currently thought not to cause significant myocardial depression. Intravenous sotalol administration has minimal effects on resting stroke volume, although heart rate and consequently cardiac output are significantly decreased. Systolic blood pressure decreases, with a minimal change in diastolic or mean pressure. Hemodynamic effects are usually seen within 15 to 20 minutes of administration. Hemodynamic indexes are maintained even in patients with mildly depressed ejection fractions (mean ejection fraction of 43 +/- 15%) after oral sotalol administration. Although heart rate decreases, cardiac index is unchanged because of a significant increase in stroke volume index. The latter results from an increase in preload (secondary to bradycardia) and a decrease in afterload. Sotalol is well tolerated, although occasionally it may cause worsening heart failure. This is seen in patients with markedly depressed left ventricular function and inadequate cardiac reserve characterized by an inability to increase stroke volume and cardiac output with exercise. Long-term (1-year) patient follow-up reveals no significant hemodynamic deterioration from initial values obtained after oral administration.

Effects of beta-adrenergic blockade on nitroglycerin-induced augmentation of regional coronary blood flow in patients

Although beta-adrenergic blockade may increase coronary vascular resistance in some patients with severe ischemic heart disease, the effects of beta blockade on the nitroglycerin (NTG)-induced augmentation of coronary blood flow have not been elucidated. Therefore, systemic hemodynamic and anterior left ventricular regional coronary blood-flow (thermodilution) data were measured during administration of NTG into the left coronary artery, before and 10 min after intravenous propranolol (0.1 mg/kg) in 22 patients. Six patients (Group 1) had normal left coronary arteries and nine (Group 2) had severe coronary artery disease with at least greater than 70% narrowing of the left anterior descending artery. In seven additional patients (three without and four with greater than 70% left anterior descending coronary artery disease), measurements were obtained with constant-paced heart rates (Group 3). Before beta blockade, NTG (200 mcg) significantly increased anterior regional great-vein flow [for Group 1, 84 +/- 38% (81 +/- 20 to 140 +/- 60 ml/min); Group 2, 39 +/- 41% (61 +/- 26 to 83 +/- 38 ml/min); and Group 3, 87 +/- 55% (75 +/- 36 to 144 +/- 86 ml/min)]. In Groups 1 and 2, beta-adrenergic blockade reduced heart rate 10% (p less than 0.01) but did not affect mean arterial or pulmonary artery pressures.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of beta blockade on systolic and diastolic left ventricular function at rest and during exercise in patients with chronic stable angina pectoris

This study examined the effects of beta blockade with betaxolol, a cardioselective, lipid-soluble, beta-adrenergic-blocking agent, on rest and exercise systolic and diastolic left ventricular function in 15 patients, aged 40 to 70 years (mean = 52), with chronic stable angina pectoris. Each patient underwent three upright exercise studies at identical workloads; the first was a baseline study, the second was done 3 hours after a single oral dose, and the third was obtained after chronic therapy for 2 weeks. Beta blockade was evident by significant decreases in heart rate, systolic blood pressure, and diastolic blood pressure at rest and during exercise (p less than 0.04). Although there were no significant changes (at rest or during exercise) in mean left ventricular ejection fraction and peak filling rate, individual variations were seen after 3 hours and 2 weeks of therapy. During chronic therapy, the peak filling rate increased in three patients, decreased in five, and remained unchanged in seven. Also, discordant changes in systolic and diastolic functions were seen at rest and during exercise during both acute and chronic therapy. Thus, although acute and chronic beta blockade produces no significant changes in mean measurements of diastolic and systolic left ventricular performance, individual variations and discordant results are seen in many patients. The acute effects are generally consistent with the chronic effects, but exceptions are present.

Improvement by oral metoprolol of exercise-induced ischemic dysfunction in patients with coronary heart disease

The effect of metoprolol on global left ventricular function during exercise was analyzed with nuclear ventriculography in 17 patients with ischemic heart disease. All had stable angina pectoris and ST-segment depression of more than 0.1 mV during treadmill exercise when not taking metoprolol. Each patient was stressed with supine bicycle exercise to the same load on a maintenance dose of metoprolol (100 mg X 2/day) and on a second occasion without the drug, the two being separated by 7 days. The mean heart rate and systolic blood pressure were significantly reduced both at rest and exercise with metoprolol. There was no significant difference of rest left ventricular ejection fraction with or without metoprolol. At exercise, however, every patient showed improvement of left ventricular function, the average left ventricular ejection fraction increasing by 14% (+/- 6) relative to the same exercise without metoprolol (p less than 0.001). We conclude that chronic metoprolol treatment in patients with ischemic heart disease can ameliorate left ventricular dysfunction induced by exercise and may thereby reduce myocardial ischemia.

Effect of beta blockade with betaxolol on left ventricular systolic function in chronic stable angina pectoris and left ventricular dysfunction

To assess the effect of beta blockade on left ventricular (LV) performance in patients with LV dysfunction and stable angina pectoris, 18 subjects taking a placebo followed by incremental doses of the cardioselective beta-adrenergic blocking agent betaxolol (5, 10, 20, 40 and 80 mg/day) were studied. The study ended with the achievement of optimal clinical beta blockade (heart rate at rest 50 to 60 beats/min, a 20% or smaller increase in heart rate during stage 1 of symptom-limited treadmill exercise using the modified Bruce protocol). Optimal clinical beta blockade produced a decrease in mean frequency of angina, from 6.8 +/- 1.7 to 0.7 +/- 0.8 episodes per week (p less than 0.0005) and an increase in mean treadmill exercise capacity, from 3.1 +/- 1.7 to 7.7 +/- 2.8 minutes (p less than 0.0005). LV systolic function was assessed at rest and during symptom-limited exercise with radionuclide left ventriculography. Mean LV ejection fraction (EF) during therapy with placebo was 39 +/- 7% at rest and 40 +/- 8% at peak exercise. Mean LVEF during optimal clinical beta blockade was 43 +/- 11% at rest and 45 +/- 10% at peak exercise. Neither of these changes was statistically significant. No patient had clinical or radiographic signs of LV failure. The results suggest that optimal clinical beta blockade with betaxolol, in doses sufficient to significantly reduce the frequency of angina and improve exercise capacity in patients with stable angina pectoris and mild to moderate LV systolic dysfunction, does not cause significant deterioration of LV systolic function or produce LV failure.

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.

Beneficial effects of high-dose diltiazem in patients with persistent effort angina on beta-blockers and nitrates: a randomized, double-blind, placebo-controlled cross-over study

The effects of orally administered diltiazem combined with maximally tolerated doses of beta-blockers and nitrates were assessed in 12 patients, who during stress testing exhibited persistent effort angina and continued objective evidence for inducible myocardial ischemia. Patients performed multistage semisupine exercise on a bicycle ergometer during equilibrium-gated radionuclide angiography after consecutive 2 week treatment periods of placebo or diltiazem 90 mg qid (mean dose 340 mg/day) combined with maximally tolerated propranolol (mean dose 178 mg/day) and isosorbide dinitrate (mean dose 137 mg/day). All medications (including diltiazem or placebo) were administered four times daily for the duration of the study. Diltiazem or placebo was administered according to a double-blind design, with randomized cross-over at the end of each 2 week treatment period. The average number of angina attacks decreased during the double-blind cross-over phase of the trial (7 +/- 7 episodes/week at baseline vs 4 +/- 3 on placebo vs 2 +/- 2 on diltiazem; p = .08). Angina pectoris was abolished during peak exercise in eight of 12 patients on diltiazem (p less than .05 vs placebo). Diltiazem increased total exercise duration from 276 +/- 92 to 310 +/- 78 sec (p less than .005 vs baseline). Diltiazem likewise increased the time to onset of angina from 231 +/- 84 sec at baseline to 305 +/- 77 sec (p less than .005), as well as the time to the onset of 1 mm ischemic ST segment depression (p = .01). Diltiazem decreased heart rate at rest, during submaximal workload, and at peak exercise (p less than .05), and decreased systolic blood pressure at peak exercise only (p less than .05). A significant decline in rate-pressure product at submaximal and peak exercise was noted (p less than .05). At any given workload there was significantly less ST segment depression during submaximal (p = .05) and peak exercise (p less than .025).(ABSTRACT TRUNCATED AT 250 WORDS)

Hemodynamic effects of nitroglycerin combined with diltiazem in patients with coronary artery disease

Resting coronary and left ventricular hemodynamic effects of diltiazem and nitroglycerin, given intravenously in combination, were studied in 12 patients with coronary heart disease. Results observed with this combination were compared with those in seven patients given diltiazem initially (group I) and five patients given nitroglycerin initially (group II). The diltiazem-nitroglycerin combination reduced systolic blood pressure 27 percent (p less than or equal to 0.05) with no significant change in heart rate to affect a 22 percent (p less than or equal to 0.05) decrease in the rate-pressure product. Left ventricular end-diastolic pressure (-36 percent) and dp/dt (-6.4 percent) both declined (p less than or equal to 0.05). Coronary flow and cardiac output were both maintained. Diltiazem alone and nitroglycerin alone also reduced systolic pressure and the rate-pressure product but to a lesser degree than the combination. Diltiazem did not significantly affect left ventricular end-diastolic pressure and dp/dt. Nitroglycerin reduced left ventricular end-diastolic pressure to an extent similar to the reduction produced by the combination but increased heart rate whereas this determinant of myocardial oxygen demand did not increase significantly with the combination. These findings suggest that the combination of diltiazem and nitroglycerin produces a greater reduction in myocardial oxygen demand than either drug alone. In addition, the combination maintains coronary blood flow without increases in determinants of myocardial oxygen demand. This potentially beneficial drug combination warrants further trial in patients with myocardial ischemia.

Three-dimensional analysis of regional myocardial function in response to nitroglycerin in patients with coronary artery disease

Biplane cineventriculography was performed at rest and after sublingual nitroglycerin in 13 patients with coronary artery disease. In six patients (responders), there was a significant increase in ejection fraction [40 +/- 5 to 52 +/- 4% (p less than 0.001)], while in the other seven (nonresponders), there was no alteration in ejection fraction. To evaluate the extent of regional myocardial response to nitroglycerin, the contractile pattern of the regional myocardium over the entire ventricular surface was analyzed using a computer-generated three-dimensional model. The spatial coordinates that define the elliptic ventricular surface on a given horizontal plane cross section of the chamber were determined by four counter values in the two orthogonal silhouettes. Then, 32 points at equal angles around the center of gravity of the end-diastolic cavity were generated to form the border image. Repetition of this process for 16 successive cross sections allowed for reconstruction of the ventricular surface by the sequence of 32 X 16 (512) points. The regional wall motion was expressed as the percent change of the radial length, drawn from the center of gravity to each surface point. There was significant heterogeneity in regional response to nitroglycerin. In the responders, the normally contracting area was significantly increased (from 16.5 +/- 16.0 to 36.2 +/- 14.9% of the total surface area, p less than 0.001), largely mediated by the greater improvement in segmental shortening of each graded contractile pattern relative to its deterioration. In the nonresponders, a lessening of the severe dysfunction of the given area was associated with significant deterioration of segmental shortening of the other normally contracting area (49.1 +/- 19.7% of the area with a contractile pattern of grade 5 had deteriorated, p less than 0.05). Thus, the ratio of the area with respective graded segmental shortening was virtually unchanged. These differences in response of the ischemic ventricle to nitroglycerin appeared to be related to the development of adequate coronary collateral vessels as well as to an interaction of changes in preload and afterload.

"Maximal" drug therapy is not necessarily optimal in chronic angina pectoris

Beta-adrenergic blocking agents, nitrates and calcium channel antagonists are effective in treating angina pectoris, but much remains unknown about how they act in combination. Consequently, treadmill exercise was used to assess the relative efficacy of nifedipine or isosorbide dinitrate, or both, in 19 patients with stable angina receiving propranolol. Propranolol therapy was continued and either placebo, nifedipine (20 mg), isosorbide dinitrate (20 mg) or both drugs were given randomly 1 1/2 hours before exercise in a double-blind trial. In 16 patients who completed the protocol, heart rate at rest during propranolol therapy was 53.7 +/- 1.9 beats/min (mean +/- standard error of the mean); it increased 4.6 +/- 1.2 beats/min with the addition of nifedipine (p less than 0.01), but was unchanged with isosorbide dinitrate or both combined. Compared with values during treatment with propranolol alone, systolic blood pressure at rest decreased with each vasodilator individually and when combined. Rate-pressure product at maximal exercise was the same with all combinations. Exercise duration was 467 +/- 50 seconds with propranolol, increased to 556 +/- 47 seconds with isosorbide dinitrate (p less than 0.05) and to 636 +/- 50 seconds with nifedipine (p less than 0.001). Exercise duration with all three drugs was 597 +/- 47 seconds (p less than 0.01 compared with propranolol alone). The improvement with nifedipine was greater than with isosorbide dinitrate (p less than 0.05) but exercise duration was not significantly different with the combination of these drugs than when either drug was used alone.(ABSTRACT TRUNCATED AT 250 WORDS)

Relation between functional response to nitroglycerin and extent of myocardial necrosis in dogs: mapping of the left ventricle by 2-dimensional echocardiography

The relation between functional response to brief nitroglycerin infusions and extent of myocardial damage was studied sequentially in closed-chest dogs with acute occlusion of the left anterior descending coronary artery. Two-dimensional echocardiography was used to derive segmental left ventricular (LV) function (systolic fractional area change and systolic wall thickening), and this function was compared with the extent of necrosis measured 5 hours after occlusion in equivalent segments of corresponding pathologic slabs. Two-dimensional echocardiographic study before the dogs were killed indicated that remote nonnecrotic segments always responded to nitroglycerin by significant augmentation of segmental LV function. Segments in which necrosis was less than 40% showed a significant nitroglycerin-induced potentiation in segmental LV function. In contrast, segments in which necrosis was greater than 60% had no potentiation with nitroglycerin. In those segments in which eventual necrosis was 60 to 80%, significant nitroglycerin-induced augmentation in segmental LV function was observed only before and 30 minutes after the coronary occlusion. When the degree of necrosis was greater than 80%, no significant potentiation of segmental LV function was observed even as early as 30 minutes after occlusion. Thus, the degree of nitroglycerin-induced potentiation of segmental cardiac function is closely associated with the extent of myocardial necrosis in the particular ventricular segment. Two-dimensional echocardiography coupled with a nitroglycerin potentiation test might be useful for assessment of the viability of ischemic myocardium.

Comparative effects of nitroglycerin, nifedipine and metoprolol on regional left ventricular function in patients with one-vessel coronary disease

To compare acute effects of nitroglycerin (0.8 mg sublingually), nifedipine (5 ng/kg/min i.v.) and metoprolol (0.15 mg/kg i.v.) on normal, ischemic and scarred myocardial segments in man, we performed simultaneous hemodynamic and radionuclide measurements of left ventricular functions. Sixteen patients with isolated left anterior descending (LAD) disease were studied at rest and during exercise. Nine patients had angina and exercise-induced ischemia (LAD stenosis) and seven patients had previous transmural myocardial infarction and no ischemic changes during thallium imaging (LAD occlusion). The effects of the drugs on regional ejection fraction of the involved anteroseptal region and the normal posterolateral area were compared. Global ejection fraction at rest did not change after nitroglycerin, increased after nifedipine and decreased after metoprolol. In patients with ischemia, the exercise ejection fraction improved after all drugs due to increased regional ejection fraction in ischemic segments: i.e., a regional antiischemic effect evidenced by improved regional function could be demonstrated with all three agents. Regional ejection fraction increased from 35.8 +/- 19.5% to 66.2 +/- 15.2% (+/- SD) after nitroglycerin (p less than 0.001), to 61.7 +/- 8.7% after nifedipine (p less than 0.001), and to 48.4 +/- 7.0% after metoprolol (p less than 0.01). In regions of myocardial scar, regional ejection fraction was not changed after any drug. In normal areas, regional ejection fraction remained unchanged after nitroglycerin and nifedipine, but decreased after metoprolol. Despite similar antiischemic effects of all three drugs, underlying hemodynamic mechanisms were quite different and may provide a rationale for combined forms of treatment. These results may help to select optimal drug combinations to improve myocardial performance in patients with chronic ischemic heart disease.

Effects of propranolol on resting and postextrasystolic potentiated left ventricular function in patients with coronary artery disease

The effect of propranolol on global and segmental left ventricular function at rest and after postextrasystolic potentiation was studied in 12 patients with chest pain. Heart rate was controlled with atrial pacing, and left ventricular cineangiograms were performed before and after 0.15 mg/kg of propranolol. During each ventriculogram a premature ventricular stimulus was introduced by means of a programmed stimulator. Propranolol decreased global left ventricular ejection fraction from 64 +/- 4.5 to 58 +/- 4.6 (p less than 0.03). Postextrasystolic potentiated global ejection fraction was not affected by propranolol (78 +/- 3.5 vs 73.6 +/- 3.4; p = NS). The area ejection fraction of the anteroapical region was decreased after propranolol (64 +/- 4.8 vs 52 +/- 6.5; p less than 0.01); however, the postextrasystolic potentiated area ejection fraction was not affected by propranolol (78 +/- 2.6 vs 71 +/- 4.6; p = NS). Frame by frame analysis of the ventriculograms demonstrated that propranolol depressed global and segmental left ventricular function by affecting the second one-third ejection fraction without influencing the first or third one-third ejection fraction. Propranolol has a small depressant effect on global and segmental left ventricular function in patients with coronary artery disease. Postextrasystolic potentiated global and segmental left ventricular function and early systolic ejection phase indices are not altered by propranolol and therefore may be useful in assessing left ventricular function in patients with coronary artery disease who are taking propranolol.

Reversal of regional myocardial depressant effects of propranolol with nitroglycerin

Use of propranolol in acute myocardial infarction is limited by its cardiodepressant effects. The effects of nitroglycerin (0.4 mg intravenously) on regional myocardial dysfunction produced by total or partial (50 percent) coronary occlusion and intravenous administration of propranolol (1.0 mg/kg) were evaluated using pairs of ultrasonic crystals implanted subendocardially in the nonischemic and ischemic zones in 14 open chest dogs. During partial coronary occlusion, systolic shortening (% delta L) in the ischemic zone decreased from 20.9 +/- 5.3 to 7.2 +/- 6.4 (p less than 0.001). Propranolol did not change it significantly. Nitroglycerin increased % delta L from 6.7 +/- 4.5 to 11.2 +/- 5.3 (p less than 0.01). The nonischemic zone was unaffected by partial coronary occlusion but showed a decrease in % delta L from 18.6 +/- 6.2 to 15.6 +/- 5.1 (p less than 0.01) with propranolol. Nitroglycerin increased % delta L from 15.6 +/- 5.1 to 17.3 +/- 5.9 (p less than 0.02). During total coronary occlusion, nitroglycerin administration after propranolol improved % delta L in the nonischemic but not in the ischemic zone. Nitroglycerin caused a significant decrease in left ventricular systolic and end-diastolic pressures. Heart rate remained unchanged. It is concluded that nitroglycerin reversed myocardial depressant effects of propranolol in both the partially ischemic and the nonischemic zones after acute coronary occlusion.

Effect of oral propranolol on rest and exercise left ventricular ejection fraction, volumes, and segmental wall motion in patients with angina pectoris. Assessment with equilibrium gated blood pool imaging

The effect of oral propranolol on left ventricular ejection fraction, left ventricular volumes, cardiac output, and segmental wall motion was assessed with multigated blood pool imaging both at rest and during supine exercise in 15 patients with angina pectoris. Propranolol had no effect on resting left ventricular ejection fractions. Before propranolol, they did not change during exercise, whereas after propranolol the ejection fractions increased slightly. Exercise left ventricular ejection fractions increased with propranolol in three patients with resting left ventricular ejection fractions of less than 40 per cent. More specifically, left ventricular end-diastolic volume index, end-systolic volume index, stroke volume index, and cardiac index were not altered significantly at rest or during exercise by propranolol. Exercise left ventricular ejection fractions were increased in five and unchanged in eight patients by propranolol. Those patients with increases in left ventricular ejection fractions had a greater change in left ventricular end-diastolic volume indices and a greater change in left ventricular end-systolic volume indices during exercise while on propranolol. Left ventricular segmental wall motion was not altered significantly during exercise by propranolol. We conclude that: (1) Left ventricular functional responses to propranolol during exercise are heterogeneous and not easily predicted; (2) propranolol causes no consistent deterioration in exercise left ventricular ejection fraction even in patients with resting ventricular ejection fractions less than 40 per cent; (3) increased exercise left ventricular ejection fraction with propranolol is contributed to by significant increases in end-diastolic volume during exercise; and (4) gated blood pool imaging is a useful method for characterising rest and exercise left ventricular ejection fractions and left ventricular volumes during propranolol therapy.

Pharmacologic intervention in cardiovascular nuclear medicine procedures

Relevant questions in ischemic heart disease are (1) what is the ischemic threat? (2) What is the extent of ventricular dysfunction? (3) Is the observed dysfunction reversible? Exercise testing can help to identify the ischemic threat. Catheterization studies have shown that resting ventricular dysfunction can be reversed in some patients through pharmacologic or surgical intervention. However, improved ventricular performance in ischemic heart disease may be achieved through a variety of mechanisms. Insight into all components of cardiac performance (regional and global contractillity, preload, afterload, and heart rate) and myocardial perfusion may be required to adequately describe the influence of intervention. Exercise radionuclide ventriculographic studies have demonstrated that stress-induced ventricular dysfunction can be reversed through surgical and pharmacologic intervention. Studies at rest have demonstrated that radionuclide techniques can detect drug-induced changes in ventricular performance in groups of patients. The challenge to cardiovascular nuclear medicine is the prospective identification of patients who would benefit most from aggressive intervention aimed at preventing or reversing ischemic ventricular dysfunction.

Hemodynamic effects of molsidomine at rest and during submaximal and maximal exercise in patients with coronary artery disease limited by exertional angina pectoris

To analyze the mechanisms of action of molsidomine, a new antianginal drug, 10 patients with coronary artery disease and exertional angina pectoris were studied. Hemodynamic measurements were made at rest, during submaximal exercise and during angina-limited exercise before and 1 hour after intravenous administration of 2 mg of molsidomine. When angina pectoris was prevented after the drug was given (6 of 10 patients), the exercise intensity was increased until the recurrence of angina (3 patients) or until exhaustion (3 patients), and hemodynamic data were recorded at this higher exercise capacity. At rest and during submaximal exercise, molsidomine increased heart rate and decreased cardiac output and mean systemic and pulmonary arterial pressures. The prevention of angina pectoris was attended by lower mean systemic and pulmonary arterial pressures and pressure-rate product; cardiac output and heart rate were unchanged. The greater exercise capacity (+26 percent) after molsidomine was attended by increases in maximal cardiac output (+19 percent) and in arteriovenous oxygen difference (+6 percent); the maximal pressure-rate product was unchanged and systemic vascular resistance was lower. The mechanisms of action of molsidomine are very similar to those of nitrates and imply a decrease in venous and arterial tone. Molsidomine deserves further study in patients with angina or congestive heart failure.

Use of catheter-tip velocity--pressure transducer to evaluate left ventricular function in man: effects of intravenous propranolol

A catheter-tip velocity transducer with two high-fidelity pressure manometers was used to evaluate the left ventricular (LV) hemodynamic effects of intravenous propranolol (10 mg). Nine patients without clinical evidence of heart failure were studied. Pulsatile ascending aortic blood flow velocity and pressure and LV pressure were measured continuously during drug administration. Beat-to-beat changes in stroke volume index, stroke work index, LV end-diastolic pressure, maximum blood flow velocity and acceleration, and maximum LV dP/dt were determined. Propranolol produced a decrease in maximum blood flow velocity (from 58 +/- 4.7 to 42 +/- 5.1 cm/sec, p less than 0.002), and acceleration (from 1181 +/- 130 to 847 +/- 117 cm/sec2, p less than 0.002, max dP/dt (from 1361 +/- 70 to 1146 +/- 63 mm Hg/sec, p less than 0.002), stroke volume index (from 47 +/- 3.0 to 38 +/- 3.2 ml/m2, p less than 0.002) and total stroke work index (from 702 +/- 33 to 603 +/- 44 mJ/m2 p less than 0.04), with little change in mean aortic pressure, peak systolic pressure and LV end-diastolic pressure. Depression in myocardial function was detectable within 1 minute after initiation of propranolol and persisted when negative chronotropic effects were eliminated by atrial pacing. The multisensor catheter technique allows rapid and safe detection of changes in cardiovascular function during propranolol administration in conscious man.

Assessment of cardiac performance with quantitative radionuclide angiocardiography. Effects of oral propranolol on global and regional left ventricular function in coronary artery disease

The effect of incremental dosages of oral propranolol (mean peak dose of 165 +/- 13 mg/day) of left ventricular ejection fraction, ejection rate and regional wall motion was studied sequentially in 22 stable, resting patients with coronary artery disease using a geometry-independent first-pass radionuclide angiocardiographic technique. All patients improved clinically, in association with a fall in heart rate and therapeutic serum propranolol levels. No significant changes were noted in ejection fraction, ejection rate or regional wall motion. No patient developed a new regional wall motion disturbance. Thus, oral propranolol administered at clinically effective antianginal dosages in patients with stable coronary artery disease does not appear to have significant deleterious effects on resting left ventricular performance.

Oral propranolol treatment in infants and children

To determine the effectiveness of oral propranolol in children, we administered 0.5 to 4.0 mg/kg/day of the drug to 64 children (age one day to 20 years); 41 with cardiac dysrhythmias, six with isiopathic hypertrophic subaortic stenosis, and 17 with paroxysmal hypoxemic spells associated with right ventricular infundibular obstruction. A new liquid form of propranolol (10 mg/ml) was administered to 37 of the younger patients, and tablets were given to the other 27. Propranolol improved the dysrhythmia in 31 of 41 patients, being notably effective in supraventricular tachycardia and ventricular tachycardia associated with a prolonged QT interval. The drug also eliminated symptoms attributed to IHSS in six of six patients and abolished hypoxemic spells in 12 of 17. The liquid and tablets were equally effective; and the liquid had the advantage of allowing for accurate dose changes in younger children. We conclude that oral propranolol is an excellent drug for use in pediatric patients with certain types of cardiac disease.

Nitroglycerin and propranolol on myocardial O2 consumption during myocardial ischemia

The effects of i.v. and intracoronary (i.c.) nitroglycerin, i.v. propranolol, and the combination of propranolol and nitroglycerin on myocardial oxygen consumption (MVO2) and lactate utilization were studied in situ ischemic working dog hearts. I.v. nitroglycerin reduced MVO2 9% which was associated with the peripheral vasodilatory actions of the drug. I.c. nitroglycerin which had no detectable effects on the peripheral vasculature had no significant effect on MVO2. I.v. propranolol caused an 8% reduction in MVO2 and this action was associated with a negative chronotropic and a slight negative inotropic effect. However, the combination of propranolol and nitroglycerin which was more effective than either drug alone, reduced MVO2 18% thereby indicating that the effects of the two drugs on oxygen consumption are additive. These results support the concept that the reduction of MVO2 seen with nitroglycerin is principally due to peripheral vasodilatory actions of the drug while that seen with propranolol is due to that drug's effect on the heart and the effects of the two agents are complementary.

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.

The effect of nitroglycerin upon pulmonary and left atrial pressures in patients with mitral stenosis

In all nine patients studied with mitral stenosis and no evidence of left ventricular failure, nitroglycerin caused a decrease in pulmonary arterial, left atrial, and left ventricular pressures and pulmonary vascular resistance. The decrease in left atrial pressure was attributable to the combination of a reduction in left ventricular filling pressure and a reduction in mitral valve gradient. While there was no significant mean change in heart rate, cardiac index, or mitral valve flow, there was a significant correlation between a decrease in each of these determinants of mitral valve gradient and the observed decline in left atrial pressure in individual patients. However, even those patients who had an increase in heart rate or cardiac output, either of which normally aggravates pulmonary congestion in mitral stenosis, had a decrease in their pulmonary and left atrial pressures in response to TNG. It is likely that nitroglycerin reduced pulmonary and left atrial pressures by either (1) systemic venous dilatation, causing a reduction in right heart filling and pulmonary blood volume, or (2) pulmonary arteriolar and venous dilatation, causing a decrease in pulmonary vascular resistance and an increase in pulmonary vascular compliance. Because of the efficacy of TNG in lowering pulmonary and left atrial pressures in this study, TNG may prove useful in the clinical management of symptomatic pulmonary congestion in mitral stenosis.

Effects of nitroglycerin on the major determinants of myocardial oxygen consumption. An angiographic and hemodynamic assessment

A direct and quantitative study of the effects of sublingually administered nitroglycerin on the major determinants of myocardial oxygen consumption was carried out in 10 patients, 7 with coronary artery disease. Left ventricular wall tension, estimates of the contractile state and heart rate were studied directly using simultaneous pressure measurements and angiographically obtained volume determinations. The peak systolic left ventricular wall tension decreased 15 percent after administration of nitroglycerin, suggesting a diminished myocardial oxygen requirement. Increased myocardial oxygen requirements were suggested by the occurrence of both positive chronotropic and inotropic effects. Heart rate increased 15 percent. The mean circumferential fiber shortening velocity increased 26 percent and the ejection fraction 30 percent; these findings, in association with a 23 percent reduction in left ventricular end-diastolic volume, were considered consistent with an increase in the contractile state. The mechanism of action of nitroglycerin seems to relate best to the decrease in systolic wall tension. The end-diastolic tension decreased 57 percent, suggesting the possibility that diastolic coronary blood flow may be augmented by diminished extravascular resistance to flow.

Nitroglycerin in experimental myocardial infarction. Effects on regional left ventricular length and tension

Controversy has existed concerning the value of nitroglycerin therapy in acute myocardial infarction. With use of Walton-Brodie strain gauge arches and mercury-in-Silastic segment length gauges, the effects of nitroglycerin (30 mug/kg intravenously) were studied on local tension and length characteristics of the ischemic, border and nonischemic zones of the left ventricle in 10 open chest dogs. In the nonischemic zone total tension increased to 144.8 +/- 13.6 (mean +/- standard error of the mean) percent (P less than 0.005) of control levels, and segment length decreased to 79.4 +/- 4.4 percent (P less than 0.01) with infusion of nitroglycerin 15 to 30 minutes after coronary ligation. Changes were similar in the groups given nitroglycerin 45 to 60 minutes and 2 to 3 hours after ligation. The border zone exhibited an increase in total tension to 132.3 +/- 8.4 percent (P less than 0.005) of control level and a decrease in segment length to 79.0 +/- 2.4 percent (P less than 0.001) in the 15 to 30 minute group. In the 45 to 60 minute group, tension increased to 117.9 +/- 4.8 percent (P less than 0.005), whereas length decreased to 86.8 +/- 1.4 percent (P less than 0.001); and in the 2 to 3 hour group tension increased to 124.9 +/- 6.0 percent (P less than 0.005), and length decreased to 91.9 +/- 3.5 percent (P less than 0.001). The decrease in magnitude of responsiveness in the 45 to 60 minute and 2 to 3 hour postligation groups compared with the 15 to 30 minute postligation group was highly significant (P less than 0.005). The central ischemic zone showed no significant change in tension or length in any group. Maximal response to nitroglycerin administration in both tension and length parameters was observed within 30 to 60 seconds and was concomitant with a decrease in systolic pressure to 73.3 +/- 1.9 percent (P less than 0.001) and an increase in heart rate to 107.2 +/- 1.0 percent. Nitroglycerin improves the contractile performance of the nonischemic and border zones after coronary occlusion without affecting the central ischemic zone. However, the border zone exhibits a progressive decrease in contractile response as a function of time. These data suggest that nitroglycerin has the overall effect of functionally reducing the extent of the ischemic area and strongly supports its potential clinical usefulness in acute myocardial infarction.

Influence of glyceryl trinitrate on force of contraction and action potential of guinea-pig myocardium

1. The inotropic effect of glyceryl trinitrate (GTN) was studied in guinea-pig papillary muscles and atrial strips by analysing the isometric contraction curve and the monophasic action potential (AP). 2. GTN, 7X10(-5)M in papillary muscles and at 1.4x10(-4)M in atrial strips. The maximum of the contractile force was reached in both preparations at 2x10(-4)M GTN. Positive inotropic effects were transitory (3--5 min) and were followed by marked negative inotropic effects. 3. In the presence of GTN, only 15 of 26 papillary muscles showed a positive inotropic response and there was a great variance in its intensity. Prior exposure of papillary muscles to a low GTN concentration, which by itself reduced force of contraction (like every single GTN application), was the prereqch by itself reduced force of contraction (like every single GTN application), was the prerequisite for the positive inotropic effect of a subsequent higher GTN concentration. In atrial strips the positive inotropic action was consistent and uniform. The maximum force of contraction in response to single applications of GTN was only about 50% of that in response to cumulatively increased GTN concentrations. 4. In the presence of 5x10(-4)M GTN, the tyramine concentration-effect curve was shifted to the left (by one log unit at the ED50 level). 5. Beta-Adrenoceptor blockade by(+/-)-propranolol (5x10(-6)M) or noradrenaline depletion by pretreatment of the animals with reserpine (5 mg/kg, 18--22 hrs prior to the experiment)prevented the positive inotropic effects of GTN in both preparations. Hence, the GTN-induced increase in contractile force is induced by the liberation of noradrenaline and an inhibitory effect on the monoamine oxidase (MAO) of sympathetic nerve endings might be involved. 6. In atrial preparations exposed to 5x10(-4)M GTN, time to peak force (tu) and relaxation time(t2) were shortened by 12% and 33%, respectively. Pretreatment of the animals with reserpine prevented the shortening og t1 and changed the shortening of t2 from 33% to 19%. 7. In papillary muscles, 5x10(-4) M GTN shortened t1 by 10%, while t2 was prolonged by 17% in noradrenaline-depleted, and by 36% in control muscles. Prolongation of t2 at 5x10(-4)M GTN was accompanied by an increase in the duration of the monophasic action patential (AP) in reserpine-pretreated as well as in control muscles by 12% and 26%, respectively (measured at 90% repolarization). The same GTN concentration slowed the maximum rate of depolarisiation by 32%. After 35 min the AP returned to approximately the control value. In the presence of 5x10(-4) M GTN, noradrenalin (1x10(-5)M) lengthened the AP by 38% in both, control muscles and noradrenaline-depleted preparations.