James H. Gault

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.

Assessment of Cardiac Function

Abstract In the past, assessment of cardiac function has centered on techniques that examined the hearts action as a pump. Hemodynamic analysis of cardiac function within the framework of the Fran...

Left Ventricular Performance Following Correction of Free Aortic Regurgitation

Left ventricular (LV) myocardial contractility, or inotropic state, was characterized in terms of the instantaneous relations between velocity of circumferential fiber shortening (VCF), determined cineangiographically, and LV wall tension (hoop stress), calculated from LV dimensions and pressure, in five patients before and 7 to 10 mo after aortic valve replacement for free aortic regurgitation. Preoperatively the cardiac index was reduced or the LV end-diastolic pressure was markedly increased (or both occurred) in four patients, in each of whom depression of inotropic state was documented by a reduced VCF at maximum wall tension, ranging from 0.13 to 1.07 circumferences (circ)/sec (normal, > 1.40 circ/sec) at wall tensions of 318 to 464 g/cm2 (normal, 178 to 417 g/cm2). In one patient in whom LV end-diastolic pressure and cardiac index were normal preoperatively, VCF was 1.66 circ/sec at a maximum tension of 440 g/cm2. Following operation, LV end-diastolic pressure fell in the four patients with depressed inotropic state (average decrease, 23 mm Hg) and cardiac index increased (average increase, 0.93 L/min/m2). However, no change in the tension-velocity relation was observed postoperatively, VCF ranging from 0.27 to 1.14 circ/sec in these patients, indicating that no change had occurred in the inotropic state. In addition, a fixed abnormality in diastolic LV pressure-volume characteristics, determined from preoperative and postoperative measurements of pressure and radius during diastole, had occurred in patients with depressed myocardial function. In contrast, in the patient with normal myocardial function, LV end-diastolic radius was reduced by 33% postoperatively while end-diastolic pressure was unchanged, suggesting reversal of stress relaxation, or creep, following relief of volume overload.

Mechanics of Left Ventricular Contraction in Chronic Severe Mitral Regurgitation

The mechanics of left ventricular contraction were studied during diagnostic cardiac catheterization using high-speed cineangiography in 11 patients with severe chronic mitral regurgitation. Compared with a group of previously studied normal subjects, most of the patients with mitral regurgitation demonstrated a reduced velocity of shortening (Vcf) during ejection at maximum wall stress, average = 1.01 circumferences/sec (circ/sec) (range 0.64-1.47 circ/sec). Maximum and mean Vcf values also were reduced in these patients, averaging 1.40 and 0.94 circ/sec, respectively. These findings are in contrast to those in acute experimental mitral regurgitation, and to observations of normal shortening velocities in chronic experimental volume overloading, in which left ventricular contraction velocity is augmented. Compared with normal subjects, patients with mitral regurgitation had significantly larger left ventricular end-diastolic circumferences and volumes, and higher total left ventricular stroke volumes. The mean regurgitant volume was 41% of the total stroke volume, of which an average of 46% was ejected into the left atrium prior to aortic valve opening. The ejection fraction and extent of fiber shortening were normal in all but two patients despite depressed shortening velocities in most. It is concluded that analysis of velocity in the ejecting phase of left ventricular contraction is useful in detecting apparent alterations in inotropic state in the face of the altered loading conditions accompanying chronic mitral regurgitation. Further, favorable unloading conditions early during systole in patients with mitral regurgitation appear to mask the effects of a depressed inotropic state on the pumping function of the heart.

Myocardial Perfusion Imaging with Radioactive-Labeled Particles Injected Directly into the Coronary Circulation of Patients with Coronary Artery Disease

Macroaggregated serum albumin (MAA) particles labeled with 131iodine (131I) or similar particles-labeled with 99mtechnetium (99mTc) or both types were injected directly into the coronary circulation of 29 patients at the time of conventional coronary arteriography. Radionuclide images of the distribution of these small (10-60 μ) biodegradable particles in the small vessels of the heart wall were made with a commercial Anger-type scintillation camera in much the same way as routine pulmonary perfusion scans are made. The resulting images depicted the relative regional distribution of blood flow to the myocardium in these patients suspected of having coronary artery disease. The myocardial perfusion images were of good quality and allowed gross assessment of perfusion by way of each major coronary artery. This was done by injecting 99mTc-labeled particles into the left coronary artery and 131I-MAA into the right coronary artery through the coronary artery catheter. Separate or composite images of the relative small vessel perfusion via each vessel injected were obtained by electronic pulse-height discrimination. No untoward reactions followed the intracoronary injection of the labeled particles. From our preliminary experience, we conclude that myocardial perfusion imaging in conjunction with coronary arteriography may prove to be a valuable diagnostic tool in the evaluation of the regional vascular supply to the heart in patients with coronary artery disease.

Evaluation of pulmonary arterial end-diastolic pressure as an estimate of left ventricular end-diastolic pressure in patients with normal and abnormal left ventricular performance.

It has been suggested that the pulmonary arterial end-diastolic pressure (EDP) may accurately reflect the level of left ventricular EDP, and therefore be useful in the continuous monitoring of left ventricular EDP in acutely ill patients. Accordingly, pulmonary arterial pressure was recorded simultaneously with left ventricular pressure in 24 patients with normal left ventricular function and in 26 patients with left ventricular myocardial disease and elevated EDP (range 13 to 38 mm Hg; average 22 mm Hg). In patients with normal left ventricular function, the EDPs in the left ventricle and pulmonary artery were equal (range 5 to 12 mm Hg; average 8 mm Hg; maximum difference ± 4 mm Hg). In contrast, in 20 of the patients with impaired left ventricular function, left ventricular EDP was consistently higher than pulmonary arterial EDP, exceeding the pulmonary arterial EDP by 2 to 21 mm Hg (average 8 mm Hg); in 12 of these 20 patients, the pulmonary arterial EDP was 12 mm Hg or less, the upper limit of normal for left ventricular EDP. The left ventricular diastolic pressure prior to atrial contraction correlated more closely with pulmonary arterial EDP. In six patients in whom increases in systemic arterial pressure were induced by methoxamine, and in two patients in whom spontaneous increases in systemic arterial pressure occurred, left ventricular EDP increased by 2 to 11 mm Hg (average 6 mm Hg); pulmonary arterial EDP remained unchanged or increased only slightly (less than 3 mm Hg) in six of the patients, and increased by 4 and 5 mm Hg in the two remaining patients. During increases in heart rate induced by atrial pacing, left ventricular EDP declined in 12 of 14 patients, while pulmonary arterial EDP increased, resulting in a consistent disparity in these pressures (average 11 mm Hg) at heart rates in excess of 124 beats/min.These data indicate that pulmonary arterial EDP does not provide an accurate estimate of left ventricular EDP in patients with chronic left ventricular disease, and in addition it often fails to reflect acute alterations in left ventricular EDP.

CLINICAL OBSERVATIONS ON PAIRED ELECTRICAL STIMULATION OF THE HEART. EFFECTS ON VENTRICULAR PERFORMANCE AND HEART RATE.

Abstract When the ventricle is electrically stimulated shortly after the termination of the refractory period, a propagated depolarization occurs which does not result in a clearly defined second ventricular contraction. A technic for repetitively delivering properly spaced paired electrical stimuli to the human heart is described, and the effects of paired electrical stimulation, or of coupled pacing, in ten patients are presented. By prolonging the period of time during which the ventricles were unresponsive to other stimuli, it was possible to reduce the heart rate. Slowing the heart rate was accomplished in two patients with rapid ventricular rates, associated in one with atrial fibrillation and in the other with atrial tachycardia. Paired electrical stimulation also augmented the contractile state of the myocardium. This augmentation was evidenced by increases in the rate of rise of intraventricular pressure, the mean systolic ejection rate and the rate of myocardial shortening, and is considered to be a form of sustained postextrasystolic potentiation. However, no consistent changes in ventricular end-diastolic pressure or cardiac output occurred. The potential clinical applications of this technic are discussed.

Dimensional Changes of the Human Left Ventricle Prior to Aortic Valve Opening: A Cineangiographic Study in Patients with and without Left Heart Disease

Previous studies of the dynamic geometry of the left ventricle have yielded conflicting results concerning shape changes during the preejection period. Accordingly, left ventricular dimensional changes prior to aortic valve opening in man were analyzed using high-speed biplane cineradiograms exposed in the frontal and lateral projections. In each projection the long axis and three chords perpendicular to it were measured. In six patients without left ventricular disease there was a mean decrease in equatorial diameter of approximately 1 mm before aortic valve opening (P < 0.05), without significant change in the long axis, causing an apparent volume decrease of 4.0 ml or 2.8% of end-diastolic volume (EDV). In five patients with wall motion disorders secondary to coronary artery disease the equatorial diameter decreased by an average of 1.5 mm and volume was diminished by 8.3 ml or 3.9% of EDV. In four of seven patients with primary myocardial disease, an increase in the equatorial diameter and a basal chord occurred, while the apical chord decreased, suggesting nonhomogeneous myocardial involvement. In eight patients with mitral regurgitation, the reduction in equatorial diameter averaged 2.8 mm and volume decreased by 16.7 ml or 8.0% of EDV. In normal patients the occurrence of circumferential fiber shortening prior to aortic valve opening under basal conditions can result in as much as a 9% underestimation of contractile element velocity calculated from dp/dt, whereas in patients with mitral regurgitation this figure may be as high as 31%. These studies indicate that, in man, expansion at the minor equator during the preejection period occurs only under highly abnormal conditions. They further suggest that the reductions in shape and volume prior to aortic valve opening may be significant relative to mechanical analyses of this phase of contraction.

Fatal familial cardiac arrhythmias: Histologic observations on the cardiac conduction system☆

Abstract Alternating bidirectional tachycardia leading to death during attempted suppressive therapy was observed in a 16 year old girl without prior clinical evidence of cardiac disease. At autopsy, there was fatty and mononuclear cell infiltration in the atrioventricular conduction system and the main left bundle branch. A similar arrhythmia has been documented in an 18 year old sister who died suddenly 9 months after discovery of her arrhythmia; autopsy revealed no gross cardiac abnormality although the conduction system was not studied. A brother, 21 years old, and the mother of the propositus, aged 45 years, also exhibited ventricular bigeminal rhythm, and a maternal uncle and grandmother had died suddenly, the latter with knowledge of an irregular heart beat. Q-T interval prolongation and auditory defects were not found. Histopathologic changes in the heart and in the conduction system in the propositus support the concept of the origin of the arrhythmia in degenerative change of the conduction system having a genetic base in this kindred.

Depressed inotropic state and reduced myocardial oxygen consumption in the human heart

Abstract The relation between myocardial oxygen uptake (MVO 2 ) and the mechanical properties of left ventricular contraction were studied in 14 patients with and without left ventricular dysfunction. Coronary blood flow was estimated by helium washout, and left ventricular inotropic state was characterized from the mean left ventricular circumferential fiber shortening velocity in the minor equator (mean V CF ) and the value at peak tension (V CF at max T). Ten patients with left ventricular dysfunction whose mean V CF values were less than 1 circumference/sec were compared with patients whose mean V CF values fell within the normal range. Patients with depressed shortening velocity had lower than normal average coronary blood tlow values (53 ± 3 vs. 70 ± 3 ml/100 g per min, respectively, P 2 (75 ± 5 vs. 120 ± 6 μl/100 g per beat, P 2 . However, mean V CF and V CF at max T correlated significantly with MVO 2 ( r = 0.63, P