Subtle left ventricular asynergy with completely obstructed coronary arteries

Modeling of asynchronous myocardial contraction by effective stroke volume analysis

Left ventricular (LV) regional wall motion abnormalities (RWMA) are not easily quantified. We describe a model for quantifying RWMA by referencing regional amplitude and phase angle changes to global LV systole in eight anesthetized, open-chest dogs. Regional and total LV volumes (conductance catheter), regional shortening (epicardial piezoelectric crystals), and LV pressure were measured before, during, and after transient esmolol-induced apical RWMA. Regional phase angle (alpha) was defined as the relative distance, measured in degrees, that regional minimal volume differs from global end-systole. We compared maximal stroke volume (SV) with effective SV (that portion of regional SV contributing to total LV SV). Regional effective SV was also calculated from our model as the product of cosine alpha and regional maximal SV. Esmolol delayed apical end-systolic alpha (14.3 degrees +/- 11.4 degrees versus 35.7 degrees +/- 8.0 degrees baseline versus esmolol, P < 0.05) and decreased apical effective SV (2.4 +/- 0.3 versus 1.7 +/- 0.3 mL, P < 0.05), while apical maximal SV and total LV SV were not altered. Piezoelectric crystal dimension changes mirrored regional SV changes. We conclude that effective SV and phase angle analysis are more sensitive measures of regional myocardial dysfunction when RWMA exist than are measures of maximal regional SV.

IMPLICATIONS

In a dog model of regional myocardial dyskinesis induced by esmolol, effective regional stroke volume and phase angle analyses are more sensitive measures of regional myocardial dysfunction than measures of maximal regional stroke volume that do not account for phase shifts.

Variability in frame by frame analysis of left ventricular wall motion from contrast angiograms

BACKGROUND

Measurement of the timing of left ventricular (LV) wall motion, of asynchrony, and of diastolic function from contrast angiograms requires delineation of the endocardial border frame by frame through the cardiac cycle. This study was performed to determine the magnitude of intraobserver and interobserver variability in manual border tracing, and to measure the impact of this variability on the derived functional parameters.

METHODS

The contrast ventriculograms of 25 patients with coronary artery disease (CAD) or with normal coronary arteries were analyzed frame by frame, by two observers or twice by the same observer. Motion was measured using the centerline method at each twelfth of systole and of diastole. Variability was calculated as the absolute difference between repeated measurements of: wall motion, asynchrony, and the time at which each region of the LV reached 10%, 50%, and 100% of peak contraction, and 50% of filling.

RESULTS

Intraobserver and interobserver variability in wall motion were similar, and varied with time in the cycle, and with location on the LV contour. Variability was highest at end systole, when it averaged 8% of the normal mean for wall motion. Variability in timing was highest at peak contraction; however, the variability in measuring asynchrony averaged only 18 msec.

CONCLUSION

Analysis of the magnitude and synchrony of regional LV wall motion through the cardiac cycle from contrast ventriculograms can be performed with reproducibility comparable to that at end systole.

Augmentation of mortality risk discriminating power of left ventricular ejection fraction by measures of nonuniformity in systolic emptying on radionuclide ventriculography

Employing equilibrium-gated radionuclide ventriculography in the left anterior oblique view, six geometric models and five mathematic coefficients of nonuniformity in regional left ventricular emptying were tested for their relative mortality risk-stratifying power and capacity to augment the risk-discriminating potency of the continuous and dichotomized global ejection fraction. Radionuclide ventriculography was performed an average of 7.6 days after acute myocardial infarction. All geometric models significantly separated 20 normal subjects from 137 patients with recent infarction (p less than 0.001). Cumulative mortality data demonstrated that significant independent univariate dichotomizing potency and augmentation of the mortality risk-discriminating power of the global ejection fraction were provided by models of regional emptying that 1) conformed to coronary artery perfusion areas, 2) encompassed total ventricular counts, 3) expressed variability in regional relative to global ejection fraction, and 4) simulated a pattern of emptying directed toward the center of geometry of the left ventricle. The combination of a four quadrant geometric model with axes drawn 45 degrees above the horizontal and a coefficient of variation calculated as square root of sigma(GEF - REF)2/4 x 100/GEF (where GEF = global ejection fraction and REF = regional ejection fraction) proved to be optimal. This coefficient averaged 12.2% in normal subjects and 32.2% in patients with recent acute myocardial infarction (p less than 0.001).(ABSTRACT TRUNCATED AT 250 WORDS)

Ischemic myocardial dysfunction assessed by temporal Fourier transform of regional myocardial wall thickening

A Fourier analysis including the first 20 harmonics was performed on sonomicrometric measurements of regional myocardial wall thickness in eight conscious dogs under control conditions and at four levels of ischemia produced by a hydraulic occluder on the left circumflex coronary artery. Systolic wall thickening was reduced from 26.47 +/- 6.20% (S.D.) (control) to 22.05 +/- 5.73% (mild stenosis), 17.00 +/- 5.86% (moderate stenosis), 11.46 +/- 3.56% (severe stenosis), and 3.69 +/- 2.57% (30-second occlusion), values significantly different from each other (p less than 0.01). The amplitude of the first harmonic decreased stepwise from 1.35 +/- 0.31 to 1.08 +/- 0.29 mm, 0.90 +/- 0.27 mm, 0.69 +/- 0.24 mm, and 0.43 +/- 0.12 mm, all significantly different from each other (p less than 0.05). These amplitude values correlated to percent systolic wall thickening (r = 0.894, p = 0.001). A phase shift of the first harmonic from 137 +/- 11 to 139 +/- 14 degrees, 150 +/- 15 degrees (p less than 0.05 vs control), 161 +/- 21 degrees (p less than 0.01 vs control), and 191 +/- 21 degrees (p less than 0.01 vs control and severe stenosis) correlated with the increase in time from end diastole to the point of maximum wall excursion (r = 0.662, p less than 0.001). These data indicate that the extent of ischemic regional myocardial hypokinesis can be adequately described by the amplitude of the first harmonic, and that the asynchrony of ventricular contraction and relaxation can be detected from the phase of the first harmonic.

The timing of paradoxical wall motion in ventricular aneurysms and in asynergic ventricles

The timing of paradoxical wall motion was investigated in the left ventricular cineangiograms of 15 patients in whom ventricular aneurysm was diagnosed or excluded at surgery. Eight had aneurysm and 7 had asynergic ventricles without aneurysm. Areas of paradoxical motion and inward motion were planimetered in each quarter of ejection. In both aneurysmal and asynergic ventricles paradoxical motion occurred within large akinetic areas. The extent of paradoxical motion was small, constituting only 3.4 and 2.6% of end-systolic areas. Over 80% of the maximal paradoxical motion occurred in the first half of ejection. In the latter half of ejection, further changes in paradoxical motion were small and inconsistent. There were no significant differences in the extent of quarterly paradoxical wall motion between the two patient groups. These data suggest that in the presence of marked left ventricular asynergy, the extent and timing of paradoxical wall motion from cineangiograms may not be useful in detection ventricular aneurysm.