Charles B. Mullins

Mean Velocity of Fiber Shortening A Simplified Measure of Left Ventricular Myocardial Contractility

Previously it was shown that left ventricular (LV) myocardial contractility can be assessed from the instantaneous relation between velocity of fiber shortening and maximum LV wall tension (VCF at max T). Such analysis is complex, requiring frame-by-frame correlation of LV dimensions with pressure, and a simpler approach was sought. In 50 patients the mean velocity of circumferential fiber shortening (mean VCF), determined from the systolic excursion of the LV internal minor equator obtained by cineangiography, was compared with instantaneous tension-velocity relations. In 13 subjects without LV disease, VCF at max T averaged 1.74 ± 0.31 (mean ± SD) circumferences (circ)/sec (range, 1.37-2.52); corresponding mean VCF was 1.50 ± 0.27 circ/sec (range, 1.23-2.03). In 22 patients with LV myocardial disease VCF at max T averaged 0.64 ± 0.29 circ/sec (range, 0.12-1.27); mean VCF averaged 0.68 ± 0.36 circ/sec (range, 0.15-1.29, P < 0.001 compared with normal subjects). Similar results were obtained in 15 patients with valvular lesions and an abnormal VCF at max T. Mean VCF detected impaired myocardial function in 95% of patients with abnormal instantaneous tension-velocity relations, and in the remaining 5% the amount of overlap between normal and abnormal mean VCF was slight. The extent of fiber shortening and the percent shortening of the internal diameter at the minor equator did not provide separation of normal from abnormal groups. It is concluded that the mean velocity of fiber shortening provides a simplified method of estimating LV contractility which: (1) requires analysis of only two frames of a cineangiogram; (2) allows quantitative comparison of LV myocardial contractility among patients; (3) adequately detects altered cardiac performance, even when valvular disease and myocardial dysfunction coexist.

Dimensional changes of the left ventricle during acute pulmonary arterial hypertension in dogs

Abstract Left ventricular dimensions and volumes were measured by an endocardial marker technique in eight closed chest dogs during progressive increases of 10 mm Hg in mean pulmonary arterial pressure. Right ventricular volumes were measured by biplane cineanglography. Increasing mean pulmonary arterial pressure caused a progressive increase in right ventricular volume; at a mean pulmonary arterial pressure of 60 mm Hg, right ventricular end-diastolic volume increased by 48 percent and end-systolic volume by 50 percent. Left ventricular volumes began to decrease significantly at a mean pulmonary arterial pressure of 30 mm Hg, and when a mean pulmonary arterial pressure of 60 mm Hg was reached, left ventricular end-diastolic volume had decreased by 30 percent and left ventricular end-systolic volume by 19 percent. Changes in ventricular filling pressure dlrectionally followed the volume changes of the respective ventricle. Left ventricular stroke volume decreased 45 percent at a mean pulmonary arterial pressure of 60 mm Hg but increasing heart rate prevented a decrease in cardiac output. The decrease in left ventricular volume as pulmonary arterial pressure was Increased was associated with a disproportionate reduction in the left ventricular septal-lateral axis. At end-diastole, this dimension decreased by 22 percent at a mean pulmonary arterial pressure of 60 mm Hg, the anterior-posterior axis decreased by 8 percent and the base-apex axis by 4 percent. A similar disproportionate decrease of the septal-lateral axis occurred at end-systole. Even at the modest increase in mean pulmonary arterial pressure to 20 mm Hg, only the septal-lateral dimension was significantly shortened, and the right ventricular end-diastolic volume had increased by 17 percent but left ventricular end-diastolic volume was not significantly changed. Thus, during acute pulmonary hypertension, the right ventricle progressively dilates resulting in a distinctive change in the shape of the left ventricle that suggests septal buiging and that may impair left ventricular function.

Intraaortic balloon counterpulsation in patients in cardiogenic shock, medically refractory left ventricular failure and/or recurrent ventricular tachycardia

Of the 27 patients described, 23 were in cardiogenic shock, 2 had severe left ventricular failure, and 2 had medically refractory ventricular tachycardia. Utilizing intraaortic counterpulsation, adequate systemic blood pressure was initially restored in 19 patients. Nine of these were subsequently weaned from circulatory assistance, but only three were discharged from the hospital and are currently alive. The remaining 10 patients who derived initial benefit from circulatory assistance were balloon-dependent in that they could not be weaned from circulatory assistance. Eight of these patients subsequently underwent cardiac catheterization; four had inoperable disease. The remaining four patients underwent surgery for either resection of the area of infarction and/or for myocardial revascularization; only one survived to subsequently leave the hospital. Ventricular volumes were abnormal and ejection fractions were below 30 per cent in all the patients in cardiogenic shock except one who underwent cardiac catheterization and ultimately died. Ejection fractions were greater than 30 per cent in the two patients with cardiogenic shock who were weaned from balloon support and survived to leave the hospital without surgery. Both of these patients had inferior myocardial infarction. The data obtained from this experience suggest that intraaortic counterpulsation is a very useful adjunct to currently existing medical measures to treat both cardiogenic shock and medically refractory left ventricular failure but that most patients have such extensive disease that they can neither be weaned from balloon support nor undergo successful infarctectomy or myocardial revascularization.

Ventricular conduction blocks and sudden death in acute myocardial infarction. Potential indications for pacing.

Abstract Of 425 patients with acute myocardial infarction admitted to a coronary-care unit 77 (18 per cent) had ventricular conduction blocks. Complete heart block developed in 43 per cent with right-bundle-branch block and left-axis deviation, in 17 per cent with left-bundle-branch block, and in 6 per cent without ventricular conduction blocks. In-hospital mortality was 30 per cent in patients with and 14 per cent without ventricular conduction block. Late sudden death occurred in five of six patients with right-bundle-branch block and left-axis deviation who had transient complete heart blocks during myocardial infarction, whereas eight similar patients with complete heart block with permanent pacing were alive. These findings suggest that patients with this form of block with an acute myocardial infarction should have temporary standby pacemakers inserted. If complete heart block develops in such cases in association with an acute myocardial infarction, even though transient, permanent pacing should be...

Pediatric Therapeutic Cardiac Catheterization A Statement for Healthcare Professionals From the Council on Cardiovascular Disease in the Young, American Heart Association

Improvednoninvasive diagnostic techniques have narrowed the indica-tions for diagnostic cardiac catheterization, and the laboratoryis now increasingly being used for therapeutic procedures.Concern about the appropriateness of some applications ofpediatric therapeutic cardiac catheterization has arisen recentlybecause of numerous catheter techniques, the increased num-bers of persons and centers using these techniques, and theincreased number of lesion types thought to be amenable tocatheter therapy.In comparison with diagnostic cardiac catheterization, ther-apeutic catheter procedures require more time and resources,are costlier and riskier, and demand more technical trainingand expertise. High levels of skill are required of the operatorwho performs the various therapeutic catheterization tech-niques. These procedures should only be performed in insti-tutions with appropriate facilities, personnel, and programs.

Control of Intractable Ventricular Tachycardia by Coronary Revascularization

Ventricular tachycardia (VT) is an arrhythmia that has an ischemic origin in up to 74% of cases and results in a 42 to 67% mortality when it is recurrent and paroxysmal. Present therapy is aimed at suppression of the abnormal rhythm but does not alter the prognosis of the underlying ischemic heart disease. A new concept of treatment of VT is introduced that is based on direct coronary revascularization by the aorta to coronary, saphenous vein-bypass technique. The method was successfully applied in a 61-year-old man who developed episodes of VT 2 months after myocardial infarction. Maximal medical therapy in a coronary care unit for 26 days did not abolish the arrhythmia which occurred as frequently as seven times an hour. Coronary angiography and aortocoronary bypass grafting were done when the patient developed electrocardiographic and enzyme evidence of subendocardial myocardial infarction and symptoms of cerebral ischemia. The patient remains free of arrhythmia 1 year later, and his exercise capability is now normal for his age. Follow-up coronary angiography is presented. Coronary revascularization has been shown to abolish angina pectoris. This report demonstrates that aortocoronary bypass grafting can abolish an arrhythmia of ischemic origin. When persistent or recurrent VT fails to respond to all medical therapy, direct coronary revascularization should be considered to control this ischemic arrhythmia.

Changes in left ventricular function produced by the injection of contrast media

Abstract The effect of radiopaque contrast media on left ventricular volume and function was analyzed during and after selective left ventricular injection of 1 c.c. per kilogram of contrast medium (76 per cent meglumine diatrizoate) or physiological saline. Radiopaque markers were implanted near the endocardium of the left ventricle in open-chest dog preparations. Biplane cinefluorography films were taken while monitoring left ventricular pressure and its derivative ( dp dt ), aortic pressure, and the ECG. End-systolic and diastolic volumes were calculated from the biplane cine films and matched with the simultaneous pressures. Systolic and diastolic volumes, stroke volume, peak left ventricular pressure, left ventricular end-diastolic pressure, and maximal rate of left ventricular pressure rise (max. dp dt ) were compared for 16 beats and for 15 minutes after injection of physiological saline or contrast medium. In 7 paired studies the injection of either contrast medium or saline produced an immediate increase in left ventricular end-diastolic pressure and volume, stroke volume, ejection fraction, max. dp dt , and peak left ventricular pressure, indicating a Frank-Starling effect. Thirteen to 16 beats after the injection of saline, all values returned toward control levels; whereas, after contrast medium injection, left ventricular end-diastolic pressure and volume increased further with a fall in max. dp dt , indicating a decrease in contractility. Subsequently, at 1 minute after the injection of contrast media, left ventricular contractility increased, as evidenced by a rise in max. dp dt and a fall in left ventricular end-diastolic volume. All values returned to control values after 15 minutes. Thus, the injection of either saline or contrast medium results in an immediate alteration in left ventricular function secondary to an increased volume load (the Frank-Starling mechanism). Left ventricular function returns rapidly to control level after the saline injection. After the contrast medium injection, however, the volume effect is followed first by a transient deterioration in function and subsequently bya transient increase in left ventricular function, an effect possibly resulting from changes in osmolality.

Permanent pacing in patients with transient trifascicular block during acute myocardial infarction

Patients with acute myocardial infarction and transient complete atrioventricular (A-V) block in association with right bundle branch block and left anterior hemiblock have a high incidence rate of late sudden death presumably due to recurrent A-V block. Over a 5 year period, 18 patients demonstrated right bundle branch block and left anterior hemiblock and had transient complete block during an acute myocardial infarction and survived to hospital discharge. Of six patients who did not have permanent pacing, five died suddenly (one was lost to follow-up) with a mean survival time of 2.4 months after hospital discharge. Twelve subsequent patients received permanent demand pacemakers and had a significantly improved prognosis with a mean survival time of 18 months (P less than 0.001). Six patients were still alive at an average follow-up time of 20 months. Prophylactic permanent pacing significantly improves the prognosis after acute myocardial infarction in this select subgroup of patients.

Incidence of arrhythmias induced by isometric and dynamic exercise

The incidence of arrhythmias during isometric sustained handgrip exercise and during dynamic graded bicycle exercise was compared in a group of 45 patients with various forms of heart disease on no antiarrhythmic therapy. Atrial arrhythmias were equally common during handgrip and bicycle exercise but ventricular arrhythmias were more frequent during handgrip exercise. Of the 45 patients, 38 per cent developed ventricular arrhythmias during isometric exercise, with ventricular tachycardia occurring in 15 per cent. During dynamic exercise 22 per cent of the 45 patients developed ventricular arrhythmias, with ventricular tachycardia occurring in 2 per cent. Patients with coronary artery disease and/or depressed left ventricular function developed twice the incidence of ventricular arrhythmias with isometric than with dynamic exercise. Thus, isometric exercise testing is of more value than dynamic exercise testing in unmasking latent ventricular arrhythmias in patients with heart disease.

Cardiovascular function during early recovery from acute myocardial infarction.

Fifty patients with acute myocardial infarction were studied serially to evaluate the extent and nature of functional cardiovascular impairment and the time course of recovery. Reinfarction or death occurred in six patients. Peak workload during bicycle exercise in a subgroup of 25 patients with maximal initial test and complete follow-up increased from 334 to 409 kpm/min (P < 0.01) between three and six weeks. There was further significant (P < 0.01) improvement between three and six months from 438 to 488 kpm/min. The incidence of ischemia at a constant workload decreased between three and six weeks without any significant changes in heart rate or blood pressure. Mean cardiac output during exercise at three months was 6.5 and at six months 7.8 L/min (P < 0.05). Corresponding values for stroke volume were 61 and 72 ml (P < 0.05). The data suggest that in clinically stable patients there is an early improvement of the relation between myocardial oxygen supply and demand and a late improvement of functional capacity associated with increased stroke volume and cardiac output.