Clinical improvement in hypertrophic cardiomyopathy after inferior myocardial infarction.

In cases of hypertrophic cardiomyopathy, the pathophysiologic role of the systolic pressure gradient across the left ventricular outflow tract is the subject of continued controversy. A patient with this disorder is described whose symptoms and provokable intraventricular gradient disappeared after inferior myocardial infarction. Diastolic left ventricular pressures were essentially unchanged, the isovolumic relaxation period became prolonged and the ejection fraction decreased from 0.77 to 0.61 after infarction. The peak ejection rate was unchanged, but the disappearance of systolic anterior motion of the mitral valve leaflet and obstructive manifestations may have resulted from enlarged mid to late systolic ventricular volumes. This case suggests a direct relation between symptoms and intraventricular pressure gradient in certain patients with hypertrophic cardiomyopathy.

Intraoperative measurement of pericardial constraint: role in ventricular diastolic mechanics.

The pressure of pericardial constraint was measured in 20 patients undergoing elective cardiac surgery (10 in Group I with normal cardiac size; 10 in Group II with cardiomegaly) using a catheter with a collapsible latex end balloon. Right atrial pressure and other hemodynamic variables including right ventricular stroke work index were also measured before and after the pericardium was widely opened. The pericardium was grossly normal in all patients and only small physiologic effusions were present. In Group I mean pericardial pressure was 8 +/- 2 mm Hg as was mean right atrial pressure. In Group II mean pericardial pressure was 6 +/- 2 mm Hg versus mean right atrial pressure of 10 +/- 5 mm Hg (p less than 0.05). Excluding 2 of the 20 patients with outlying data, pericardial pressure showed linear correlation with right atrial pressure (r = 0.689). In Group I right ventricular stroke work index rose from 5.0 +/- 2.0 to 6.4 +/- 2.1 g-m/m2 (p less than 0.01) after pericardiotomy with no significant increase in mean right atrial pressure; similar findings in Group II were consistent with removal of external constraint. Thus, even in the absence of an abnormal effusion the normal pericardium exerts a significant pressure on the heart, which is often similar in magnitude to right atrial pressure. In certain notable exceptions, however, right atrial pressure far exceeds pericardial pressure. Such pericardial constraint has important implications for ventricular diastolic mechanics.

Paradoxical deterioration of left ventricular asynergy after administration of nitroglycerin.

The effects of nitroglycerin on segmental asynergy were studied by 2-dimensional echocardiography. Forty-five patients with coronary artery disease and segmental wall motion abnormality at rest were examined, 31 with Q-wave and 14 with only ST-T abnormalities. Left ventricular (LV) echocardiograms were recorded from the LV apex in 4 planes, obtained by systematically rotating the transducer at 45 degrees intervals around the mitral office, using a mechanical device. Sixteen LV segments were analyzed in each patient on real-time display by 2 observers independently. The wall motion analysis was classified as normal, hypokinetic, akinetic or dyskinetic. Of 720 segments, 596 were agreed on by 2 observers in the assessment of wall motion before and after administration of nitroglycerin: 334 segments (56%) showed no change in wall motion, 206 (35%) showed improvement of wall motion and 56 (9%) showed worsening of myocardial asynergy after nitroglycerin. These data suggest that administration of nitroglycerin may result in unexpected worsening of segmental asynergy. This may be secondary to an adverse effect of a decrease in perfusion pressure in critically occluded arteries or may represent a coronary steal phenomenon.

Ventricular performance related to transmural filling pressure in clinical cardiac tamponade.

In clinical cardiac tamponade, open-catheter intrapericardial pressure (IPP) may be used to estimate left ventricular transmural filling pressure (TMFP). However, it has been suggested recently that right atrial pressure (RAP) is superior to IPP in assessing true extracardiac pressure during pericardial drainage. In 10 patients with subacute cardiac tamponade, pulmonary wedge pressure (PWP), RAP, and IPP were measured along with indexes of systolic function. To test the relative merits of IPP and RAP in assessing true pericardial pressure, three TMFP estimates were analyzed: TMFP1 = (PWP - IPP); TMFP2 = (PWP - 1/3 RAP - 2/3 IPP); and TMFP3 = (PWP - RAP). An accurate TMFP presumably should increase during pericardiocentesis and correlate with left ventricular stroke work. In addition, to test the role of preload variation in pulsus paradoxus, respiratory variation in TMFP was analyzed. In the initial tamponade state, RAP and IPP were essentially equal, so all three TMFP estimates gave equivalent results. For instance, TMFP1 averaged 4 +/- 2 mm Hg but fell to 0.2 +/- 1.3 mm Hg during inspiration (p less than .001 vs expiration) and showed beat-by-beat correlation with pulse arterial pressure. After intermediate pericardiocentesis (280 +/- 160 ml), the IPP of 6 +/- 3 mm Hg fell significantly below the RAP of 10 +/- 3 mm Hg (p less than .001), but with a 570 +/- 320 ml residual effusion suggesting continued IPP measurement accuracy. By complete pericardiocentesis (810 +/- 430 ml) there was a significant increase in TMFP1 to 8 +/- 4 mm Hg (p less than .05 vs tamponade) but not in the TMFP3 of 1 +/- 3 mm Hg. Encompassing tamponade and pericardiocentesis data, left ventricular stroke work index showed positive correlation with TMFP1 (r = .59) and TMFP2 (r = .52) but not with TMFP3. Thus cardiac tamponade often may be diagnosed with a TMFP averaging well above zero, and diastolic equalization of PWP, RAP, and IPP may be a predominantly inspiratory finding ("inspiratory tracking"). This supports the role of preload variation in the genesis of pulsus paradoxus. On the other hand, true pericardial pressure may fall substantially below RAP in the course of pericardial drainage. This may be reconciled with the concept that normal pericardial pressure nearly equals RAP by hypothesizing an increased pericardial capacity in subacute tamponade so that pericardiocentesis produces a state analogous to removal of normal pericardial constraint.

Left ventricular volume measurement by conductance catheter in intact dogs. Parallel conductance volume depends on left ventricular size.

The conductance catheter is a promising new instrument for continuously measuring left ventricular (LV) volume. Absolute LV volume (V[t]) is related to uncorrected conductance volume, B(t), according to the equation: V(t) = (1/alpha)(B(t) - alpha Vc). The alpha Vc factor represents parallel-conductance volume due to conducting material outside the LV blood pool, and may be estimated by transiently changing blood conductivity using a bolus injection of hypertonic saline. alpha is the slope in the relation between B(t) and true LV volume. We tested the assumption that alpha Vc and alpha are constant over a range of hemodynamic conditions. We performed multiple hypertonic saline alpha Vc determinations in seven intact dogs during control conditions and subsequent temporary balloon occlusions of inferior vena cava (IVCO), aorta (AO), and pulmonary artery (PAO). We also compared B(t) with simultaneous biplane angiographic LV volume during similar control and intervention conditions. The saline-derived alpha Vc was 76 +/- 2 ml during control and fell significantly by -7 +/- 2 ml during IVCO (p less than 0.001) but not during AO or PAO. According to multiple linear regression analyses, the strongest predictor of saline-derived alpha Vc was uncorrected end-systolic Bes, with a sensitivity coefficient of 0.60 +/- 0.06 ml/ml (p less than 0.001). Angiographically derived alpha Vc showed a similar dependence on Bes, with a coefficient of 0.77 +/- 0.14 ml/ml (p less than 0.001). Angiographically determined alpha also showed significant variation with hemodynamic interventions, largely reflecting an underlying dependence on alpha Vc. The variation in alpha Vc and alpha with LV size may stem from nonlinearity in the B(t)-V(t) relation. Although the conductance catheter provides a useful measure of relative LV volume, measurement of absolute LV volume over a wide hemodynamic range using constant alpha Vc and alpha factors is unrealistic. This result calls into question the current use of this technique for the measurement of the absolute end-systolic--pressure-volume relation.

Percutaneous double balloon aortic valvuloplasty in an adult patient with calcific aortic stenosis and a Bjork-Shiley prosthetic mitral valve.

Percutaneous transluminal balloon valvuloplasty is a new technique in interventional cardiology which to date has been applied successfully in the dilatation of all four cardiac valves. Although the different techniques appear to be quite effective, the safety of these procedures has not been fully explored. In particular, because of the close anatomic relationship of the aortic and mitral annuli, the safety of aortic valvuloplasty in patients with mitral valve prosthesis is unknown. Therefore, we report the applicability of a percutaneous double balloon valvuloplasty in an elderly patient with calcific aortic stenosis and a Bjork-Shiley mitral valve prosthesis.

Simplified echocardiographic measurement of the mitral anulus.

Postmortem, clinical, and experimental observations suggest an approximate elliptical shape for the mitral valve anulus, limiting the accuracy of single-diameter measurements in estimating annular area and circumference. A detailed method has been reported which uses six apical echocardiographic views at 30-degree rotational intervals to measure the mitral anulus, providing results comparable with pathologic and experimental reports. Annular data from nine normal subjects and 18 patients with dilated cardiomyopathy were analyzed to test a simplified measurement procedure. Assuming an elliptical shape, mitral annular area (MAA) and mitral annular circumference (MAC) were calculated by means of major (usually corresponding to the four-chamber view) and minor diameters from two orthogonal apical planes. Assuming a circular shape, MAA and MAC were also estimated by means of single annular diameters obtained from both an apical four-chamber and a parasternal long-axis view. Systolic and diastolic points were analyzed together, providing an n = 54 in the linear regressions. The two-plane results in MAA and MAC were nearly identical to those from the six-plane method, with very close correlation (r = 0.982 to 0.990). The single-plane results systematically overestimated MAA and MAC, with less correlation (apical, r = 0.943 to 0.963; parasternal, r = 0.852). Thus, while single-diameter measurements may correlate with global changes in annular size, the two-plane method represents a simplified but accurate method for estimating MAA and MAC in humans.