Effects of rapid digitalization on total and regional myocardial performance in patients with coronary artery disease

Combination of positive inotropic and vasodilating substances in congestive heart failure

Therapy combining vasodilators and inotropic agents is considered to be one of the most powerful means of improving cardiac function in patients with congestive heart failure (CHF). The vasodilators enhance the effectiveness of inotropic agents by providing a reduction in preload and/or afterload. Inotropic drugs with different mechanisms of action, such as digitalis glycosides, ephedrine, dopamine, dobutamine, ibopamine, terbutaline, salbutamol, pirbuterol, prenalterol, amrinone, and milrinone, have been tested in combination with vasodilators with a predominant effect on preload (nitrates, molsidomine), with a predominant effect on afterload (hydralazine, nifedipine), or with a balanced action on both arterial and venous beds (nitroprusside, prazosin, captopril), showing positive results. The problem of the combination of digitalis glycosides and vasodilators with different sites of action has been considered by our group. In 42 patients with CHF, digoxin (DIG, 0.01 mg/kg intravenously) was tested in combination with molsidomine (MLS, 4 mg sublingually) (12 patients), a nitrate-like agent with a predominant vasodilating action on the capacitance vessels, nifedipine (NFP, 10 mg sublingually) (22 patients), a Ca2+ antagonist drug with a predominant action on the resistance vessels, and captopril (CPT, 25 mg orally) (8 patients), an ACE inhibitor with a balanced effect on both preload and afterload. The combination DIG plus MLS caused a reduction in left ventricular filling pressure (LVFP) greater than that achieved with either agent alone. The hemodynamic improvement was obtained without side effects, in spite of the striking fall in preload. We stress that this investigation was performed on patients with CHF following acute myocardial infarction.(ABSTRACT TRUNCATED AT 250 WORDS)

Effect of ouabain on O2 supply/demand in normal and ischemic heart

The effect of ouabain (15 microgram/kg) on subepicardial and sub-endocardial blood flow, oxygenation, and small-vessel blood content was studied in anesthetized open chest rabbits with hearts subjected to acute coronary occlusion. 10 minutes after occlusion, blood flow was 48% lower than in the control region. Ouabain lowered blood flow significantly in the non-occluded region and insignificantly in the occluded area. Small-vessel blood content, a measure of open capillary density, was unaffected by occlusion or ouabain. After occlusion, relative tissue PO2 fell to a greater extent in the affected subendocardium than the affected subepicardium. Ouabain, therefore, appears to be well tolerated in both the control and ischemic regions in terms of oxygen supply and consumption.

Effects of digitalis on subendocardial and subepicardial dysfunction during acute ischemia

The effects of digitalis (ouabain infusion, priming dose of 10 micrograms/kg/min followed by 2.0 micrograms/kg/min) on subepicardial and subendocardial ischemic dysfunction during partial occlusion (59.4% reduction in coronary flow) and total coronary occlusion were evaluated in 14 dogs using pairs of ultrasonic crystals implanted in the epicardial and endocardial layers. After 30 minutes of partial coronary occlusion, systolic shortening in the ischemic zone decreased from 12.4 +/- 2.9% to -0.4 +/- 0.9% (p less than 0.001) in the epicardium and from 18.9 +/- 3.1% to -1.0 +/- 1.1% (p less than 0.001) in the endocardium. Ouabain infusion increased the systolic shortening from -0.4 +/- 0.9% to 10.6 +/- 3.1% (p less than 0.001) in the epicardium and from -1.0 +/- 1.1% to 17.2 +/- 3.4% (p less than 0.001) in the endocardium. The end-diastolic length did not change. In contrast, after 30 minutes of total coronary occlusion, systolic shortening in both epicardial and endocardial layers was replaced by systolic lengthening and remained unaffected by ouabain infusion in both layers. Systolic shortening in the nonischemic epicardial and endocardial layers increased consistently. We conclude that ouabain improves the contractile function of both ischemic epicardial and endocardial layers layers after partial coronary occlusion and does not worsen subendocardial ischemic dysfunction. After total coronary occlusion, however, the contraction of the ischemic zone is unaffected by ouabain.

Hemodynamic pattern following K-strophanthin in normal and coronary artery disease patients

Hemodynamic effects of K-strophanthin (0.005 mg/kg i.v.) were evaluated in 7 normal and in 13 non-failing coronary artery disease patients (CAD). Volumetric parameters were obtained by single plane left ventricular angiography. The indexes of "pump" function, the end-systolic pressure-volume relationship and the ratio of peak pressure to systolic volume were also evaluated. Heart rate was maintained constant by atrial pacing. In normal subjects K-strophanthin exerted small effects without peripheral vasoconstriction. CAD patients showed different response to K-strophanthin in vascular tone: an increase (Group 1) or a decrease (Group 2) in total systemic resistance (TSR). No significant differences were found in basal values between the two CAD groups. In Group 2 the indexes of "pump" function increased after K-strophanthin and the end-systolic pressure-volume points shifted upward and to the left, while in Group 1 no improvement in cardiac function was observed and the end-systolic pressure-volume points shifted upward and to the right. Furthermore, we found a direct significant correlation between the percent changes of TSR and end-systolic volume index, and a negative significant correlation between the percent changes of TSR and stroke volume index. Our results show that K-strophanthin in CAD non-failing patients can have either a positive effect or a lack of improvement in ventricular performance. These effects correlate with changes in total systemic resistance.

Antianginal and myocardial metabolic properties of verapamil in coronary artery disease

To determine the metabolic cost of administering an experimental calcium antagonist, verapamil, to patients with coronary artery disease, 12 such patients were studied at rest and during stress with atrial pacing before and after intravenous treatment with verapamil (bolus dose of 0.1 mg/kg body weight, followed by infusion at 0.005 mg/kg per min). The mean (+/- standard deviation) aortic pressure at rest (98 +/- 22 mg Hg), coronary sinus blood flow (88 +/- 17 ml/min) and myocardial oxygen consumption (10.7 +/- 2.4 ml O2/min) decreased to 88 +/- 20 mm Hg (p < 0.0004), 77 +/- 14 ml/min (p < 0.03) and 8.8 +/- 2.5 ml O2/min (p < 0.01), respectively, after administration of verapamil. With atrial pacing, these values were 105 +/- 25 mm Hg, 151 +/- 50 ml/min and 18.5 +/- 6.4 ml O2/min, respectively, before infusion of verapamil, and then decreased to 87 +/- 14 mm Hg (p < 0.006), 107 +/- 31 ml/min (p < 0.0002) and 13.3 +/- 4.4 ml O2/min (p < 0.001) during infusion. Angina occurred in all patients with atrial pacing before verapamil (threshold to pain: 93 +/- 67 seconds). After verapamil, the threshold to pain in six patients increased to 191 +/- 183 seconds; and no pain was experienced by the remaining six (p < 0.0005). Before administration of verapamil lactate extraction decreased from 24 +/- 9 to 10 +/- 11 percent (p < 0.0002) during atrial pacing, and 9 (75 percent) of the 12 patients exhibited electrocardiographic S-T segment depressions. After administration of verapamil lactate extraction normalized to 22 +/- 9 percent during atrial pacing, and the electrocardiogram reverted to baseline in all but one patient. These findings indicate that verapamil decreases left ventricular myocardial metabolic demands, and concomitantly greatly increases the threshold to angina.