Mechanism of early systolic closure of the aortic valve in discrete membranous subaortic stenosis

Recommendations for Multimodality Cardiovascular Imaging of Patients with Hypertrophic Cardiomyopathy: An Update from the American Society of Echocardiography, in Collaboration with the American Society of Nuclear Cardiology, the Society for Cardiovascular Magnetic Resonance, and the Society of Cardiovascular Computed Tomography

Hypertrophic cardiomyopathy (HCM) is defined by the presence of left ventricular hypertrophy in the absence of other potentially causative cardiac, systemic, syndromic, or metabolic diseases. Symptoms can be related to a range of pathophysiologic mechanisms including left ventricular outflow tract obstruction with or without significant mitral regurgitation, diastolic dysfunction with heart failure with preserved and heart failure with reduced ejection fraction, autonomic dysfunction, ischemia, and arrhythmias. Appropriate understanding and utilization of multimodality imaging is fundamental to accurate diagnosis as well as longitudinal care of patients with HCM. Resting and stress imaging provide comprehensive and complementary information to help clarify mechanism(s) responsible for symptoms such that appropriate and timely treatment strategies may be implemented. Advanced imaging is relied upon to guide certain treatment options including septal reduction therapy and mitral valve repair. Using both clinical and imaging parameters, enhanced algorithms for sudden cardiac death risk stratification facilitate selection of HCM patients most likely to benefit from implantable cardioverter-defibrillators.

A review of the in vitro evaluation of conduit-mounted cardiac valve prostheses

This review concerns the issues affecting the in vitro evaluation of conduit-mounted prosthetic heart valves at the design development stage, and the question of standardisation of testing at the quality assurance stage. Particular attention is given to areas of conduit valve development and research which have been neglected, ambiguously covered or left to the discretion of the researcher in the current standard for conventional prosthetic valves, ISO 5840.

Color-coded Doppler imaging of systolic flow patterns in hypertrophic cardiomyopathy

We studied 11 patients with hypertrophic cardiomyopathy by color Doppler echocardiography (Group I: 6 patients with outflow obstruction, and Group II: 5 patients without outflow obstruction) to assess systolic structure and function as observed by cross-sectional echocardiography in relation to the flow dynamics. The structure and function included systolic anterior motion of mitral valve (SAM), midsystolic aortic valve closure (AoC), systolic cavity obliteration and the presence and timing of mitral incompetence. Their occurrence and timing was related to presence of aortic systolic flow and presence of turbulence. While all patients in Group I had SAM and turbulence, none of the patients in Group II had SAM nor turbulence. Early mitral incompetence appearing before SAM and turbulence, occurred in all patients of Group I and in none of Group II. Midsystolic aortic valve closure was only present in Group I and blood flow was unilaterally directed so that only 60% of aortic cross-sectional area showed blood flow. We conclude that mitral incompetence in hypertrophic cardiomyopathy in early systole is common when outflow gradient is present and is independent of mitral incompetence of mid- and late systole. During SAM, turbulence in the subaortic area and mid and late mitral incompetence occurred simultaneously. The midsystolic aortic valve closure was related to the unilaterally directed blood flow through the aortic cross-sectional area.

Hemodynamics of multiple versus single 50 percent coronary arterial stenoses

The purpose of this study was to compare coronary blood flow in the presence of multiple fixed coronary arterial stenoses with that in the presence of a single stenosis of equivalent length and diameter. The study was performed using an in vitro pulse duplicating system. The aortic root section consisted of an acrylic mold of the root of the aorta of a calf. The coronary system was designed to produce coronary flow with physiological magnitudes and phasic patterns. Aortic and left ventricular pressures as well as the reduction in pressure across the coronary test section containing the stenotic segments were measured with catheter-tip micromanometers. Coronary flow was measured with a cannulating electromagnetic flow transducer. The fluid viscosity was 0.04 poise. Studies were performed sequentially with one 2 mm long arterial segment with a stenosis of 50 percent of luminal diameter, two such stenotic segments and three such stenotic segments in series. A single 4 mm long, 50 percent diameter stenotic segment and a 6 mm long, 50 percent diameter stenotic segment were also studied. The heart rate was 71 beats/min, stroke volume 80 ml and aortic pressure 140/75 mm Hg. A single 2 mm long, 50 percent stenotic segment caused a 6 percent reduction of coronary flow; three such stenoses in series caused a 19 percent reduction of coronary flow. In contrast, a single 6 mm long, 50 percent diameter stenotic segment caused only an 8 percent reduction of coronary flow. The results suggest that in a maximally dilated coronary bed, a greater reduction of coronary flow would occur in the presence of multiple short stenoses than in the presence of a single stenosis of equivalent length and diameter.

Hemodynamic determinants of the frequency and amplitude of a musical murmur produced by a regurgitant mitral bioprosthetic valve

The purpose of this study was to assess the hemodynamic determinant of the amplitude and frequency of a musical murmur produced by a regurgitant degenerated bioprosthetic valve in the mitral position. The prosthetic valve, obtained at surgery, was studied in the mitral position of an in vitro pulse duplicating system. In vitro, the valve produced a musical murmur that was caused by flutter of a flail leaflet. When the peak pressure difference between the left ventricle and left atrium was increased from 95 to 150 mm Hg, the fundamental frequency of the musical murmur increased from 91 to 187 hertz and the amplitude increased from 2,080 to 11,420 dynes/cm2. The fundamental frequency of the musical murmur was linearly related to the peak systolic pressure difference between the left ventricle and the left atrium (correlation coefficient [r] = 0.99). Similarly, the fundamental frequency of the musical murmur was linearly related to the magnitude of regurgitant flow across the valve (r = 0.99); and the regurgitant flow as expected was linearly related to the systolic pressure difference between the left ventricle and left atrium. The amplitude of the musical murmur was also related to both the peak systolic pressure difference between the left ventricle and left atrium (r = 0.99) and the magnitude of regurgitant flow (r = 0.99). These results indicate that the magnitude of regurgitant flow, determined by the systolic pressure difference between the left ventricle and left atrium, was a determinant of both the amplitude and the frequency of the musical murmur.

Mechanism of a musical systolic murmur caused by a degenerated porcine bioprosthetic valve

The cause of a musical (cooing) murmur produced by a degenerated bioprosthetic valve in the mitral position was investigated. Spectral analysis of the murmur recorded at the chest wall at the site of the maximum palpable impulse showed virtually all sound in a narrow frequency band around the dominant frequency of 158 hertz. The same valve, surgically removed and mounted in the mitral position in a pulse duplicating system, produced an audible musical murmur detected by a phonocatheter in the atrial chamber. Nearly all of the sound-pressure occurred in a narrow band of frequency around 145 hertz. High speed motion pictures (500 frames/s) showed systolic flutter of a flail leaflet. The frequency of this leaflet flutter was 142 hertz. Hot film anemometry showed minimal turbulence, all located near the margin of the regurgitant leaflet. The intensity of the murmur was unrelated to the intensity of turbulence. A second degenerated bioprosthetic valve that produced in vivo a typical blowing holosystolic mitral regurgitant murmur produced in vitro a murmur with a broad range of frequencies (20 to 500 hertz). With this valve, the intensity of the murmur was related to the intensity of the turbulence. Motion pictures showed no leaflet flutter. Flutter of an insufficient valve leaflet causing uniform and periodic high frequency fluctuating pressures therefore appeared to be the cause of the musical quality of the systolic murmur in a degenerated bioprosthetic valve.