Reliability of echocardiographic and electrocardiographic parameters in assessing serial changes in left ventricular mass

A reliable noninvasive index of left ventricular mass would be useful in following patients with valvular heart disease and left ventricular hypertrophy. We reviewed concurrent electrocardiograms and echocardiograms from 54 subjects, 39 patients with aortic or mitral valve disease and 15 normal subjects. Pre- and early postoperative echocardiographic estimates of left ventricular mass in 17 patients who had valve replacements correlated well (r = 0.96, p < 0.001) and demonstrated little change in mean values despite altered left ventricular dimensions. Echocardiographic estimates of left ventricular mass were, therefore, used as a standard for evaluating other noninvasive indices. Precordial electrocardiographic voltage showed a weak correlation with left ventricular mass in the study group as a whole (r = 0.59, p < 0.001), but no correlation in patients with volume overload (r = 0.36, p = NS). In 18 patients who had preoperative and three separate postoperative studies at least eight weeks apart, changes in left ventricular cross-sectional area (an index of left ventricular mass which corrects for changes in left ventricular volume) closely followed alterations in left ventricular mass. However, changes in posterior wall and interventricular septal thickness often resulted from altered ventricular volume and did not accurately reflect directional changes in left ventricular mass. Serial changes in electrocardiographic voltage were similarly unreliable. We conclude that left ventricular mass and cross-sectional area by echocardiography allow accurate noninvasive assessment of left ventricular mass, whereas wall thickness and electrocardiographic changes do not.     

Sources of variability in the radionuclide angiographic assessment of ejection fraction: A comparison of first-pass and gated equilibrium techniques

Measurements of ejection fractions (EF) determined by first-pass and gated equilibrium radionuclide angiography are widely believed to be equivalent. To compare these measurements in a large group of patients over a wide range of EF values, left ventricular (LV) and right ventricular (RV) EFs at rest were measured in 135 consecutive patients who underwent the 2 methods of radionuclide angiography within 1 hour: first-pass upright with a multi-crystal camera in the anterior projection and gated equilibrium supine with a single-crystal camera in the left anterior oblique projection. The population included 18 normal patients and 117 patients with various cardiac and pulmonary disorders. First-pass and gated equilibrium LVEF correlated well (r = 0.83, p <0.001), but the slope of the regression line was different from unity, with the first-pass values lower than the gated equilibrium values (0.51 ± 0.16 vs 0.56 ± 0.15, p <0.05 [mean ± standard deviation]). Among the 45 patients with a gated equilibrium LVEF of <0.50, the correlation (r = 0.84) was better than that for the 90 patients with a LVEF > 0.50 (r = 0.44, p <0.05). However, in the latter group, the correlation remained good in the 15 patients with cardiomegaly due to aortic or mitral regurgitation (r = 0.80). Inter- and intraobserver error was similar for both methods. In contrast, there was a poor correlation between first-pass and gated equilibrium RVEF, with the first-pass values higher than the gated equilibrium values (0.51 ± 0.11 vs 0.43 ± 0.11, p <0.01). Interobserver error was similar for both the methods, but intraobserver error was better for the first-pass method (p <0.05). Thus, there may be considerable variability in the radionuclide EF at rest in the same patient because of differences in the method of measurement. Caution is suggested when EF values that have been derived using different radionuclide methods are compared.     

Electrocardiographic detection of left ventricular hypertrophy using echocardiographic determination of left ventricular mass as the reference standard. Comparison of standard criteria, computer diagnosis and physician interpretation

Electrocardiographic findings of left ventricular hypertrophy were compared with echocardiographic left ventricular mass in 148 patients to assess performance of standard electrocardiographic criteria, the IBM Bonner program and physician interpretation. On echocardiography, 43% of the patients had left ventricular hypertrophy (left ventricular mass greater than 215 g). Sokolow-Lyon voltage-(S in V1 + R in V5 or V6) and Romhilt-Estes point score correlated modestly with left ventricular mass (r = 0.40, p less than 0.001 and r = 0.55, p less than 0.001, respectively). Sensitivity of Sokolow-Lyon voltage greater than 3.5 mV for left ventricular hypertrophy was only 22%, but specificity was 93%. Point score for probable left ventricular hypertrophy (greater than or equal to 4 points) had 48% sensitivity and 85% specificity, whereas definite hypertrophy (greater than or equal to 5 points) had 34% sensitivity and 98% specificity. Computer analysis resulted in 45% sensitivity and 83% specificity. Overall diagnostic accuracy of the IBM Bonner program (67%) was better than that of Sokolow-Lyon voltage (62%), but worse than the Romhilt-Estes point score (69% for greater than or equal to 4 points or 70% for greater than or equal to 5 points). Three cardiologists interpreted electrocardiograms independently and in a blinded fashion. Physician sensitivity was 56%, specificity 92% and accuracy 76%. Correlation with left ventricular hypertrophy was good (r = 0.70, p less than 0.001). It is concluded that: 1) computer diagnosis of left ventricular hypertrophy by the IBM Bonner program is no more accurate than diagnosis by Sokolow-Lyon or Romhilt-Estes criteria, and 2) physician recognition of left ventricular hypertrophy is more accurate.(ABSTRACT TRUNCATED AT 250 WORDS)     

Whole blood viscosity as a determinant of cardiac hypertrophy in systemic hypertension

The relationships among blood pressure (BP), blood viscosity and echocardiographic left ventricular (LV) muscle mass were evaluated in 24 patients with essential hypertension and in 13 normotensive control subjects. LV mass was greater in the hypertensive patients than in the control subjects (225 ± 69 vs 170 ± 31 g, p < 0.02) as was blood viscosity at a shear rate of 104 sec^?1 (4.7 ± 0.1 vs 4.3 ± 0.2 cp, p <0.005). Among the hypertensive patients, LV mass was most closely related to viscosity at 104 sec^?1 (r = 0.80, p < 0.001), whereas only weak correlations were found between LV mass and systolic or diastolic BP (r = 0.45, p < 0.05 for both). The 14 hypertensive patients with normal LV mass had viscosity similar to that in control subjects (4.5 ± 0.3 vs 4.3 ± 0.2 cp), whereas viscosity was consistently increased (5.0 ± 0.4 cp, p < 0.02) in hypertensive patients with LV hypertrophy. Thus, increased blood viscosity may be a determinant of or a response to hypertensive cardiac hypertrophy.     

Beat-to-beat left ventricular performance in atrial fibrillation: radionuclide assessment with the computerized nuclear probe

There is wide beat-to-beat variability in cycle length and left ventricular performance in patients with atrial fibrillation. In this study, left ventricular ejection fraction and relative left ventricular volumes were evaluated on a beat-to-beat basis with the computerized nuclear probe, an instrument with sufficiently high sensitivity to allow continuous evaluation of the radionuclide time-activity curve. Of 18 patients with atrial fibrillation, 5 had mitral stenosis, 6 had mitral regurgitation, and 7 had coronary artery disease. Fifty consecutive beats were analyzed in each patient. The mean left ventricular ejection fraction ranged from 17 to 51%. There was substantial beat-to-beat variation in cycle length and left ventricular ejection fraction in all patients, including those with marked left ventricular dysfunction. In 14 patients who also underwent multiple gated cardiac blood pool imaging, there was an excellent correlation between mean ejection fraction derived from the nuclear probe and gated ejection fraction obtained by gamma camera imaging (r = 0.90). Based on beat-to-beat analysis, left ventricular function was dependent on relative end-diastolic volume and multiple preceding cycle lengths, but not preceding end-systolic volumes. This study demonstrates that a single value for left ventricular ejection fraction does not adequately characterize left ventricular function in patients with atrial fibrillation. Furthermore, both the mean beat-to-beat and the gated ejection fraction may underestimate left ventricular performance at rest in such patients.     

Relation of hemodynamic load to left ventricular hypertrophy and performance in hypertension

Left ventricular hypertrophy and dysfunction in patients with hypertension are often poorly related to the level of blood pressure. To evaluate the reasons for this, 100 untreated patients (44 +/- 14 years) with essential hypertension were studied using cuff blood pressure and quantitative echocardiography to measure left ventricular mass index and end-diastolic relative wall thickness as 2 indexes of left ventricular hypertrophy. Left ventricular hypertrophy, as measured by either left ventricular mass index or end-diastolic relative wall thickness, correlated weakly with all indexes of blood pressure including systolic, diastolic, and mean blood pressure (r = 0.16 to 0.32). In contrast, end-diastolic relative wall thickness, an index which assesses the severity of concentric hypertrophy, showed a closer direct relation with total peripheral resistance (r = 0.52 p less than 0.001) and a significant inverse relation with cardiac index (r = -0.47, p less than 0.001). Left ventricular performance as assessed by fractional systolic shortening of left ventricular internal dimensions was not significantly related to left ventricular mass index, blood pressure, or peak systolic wall stress, but declined significantly with increasing mean systolic wall stress (r = -0.42, p less than 0.001) and even more with increasing end-systolic wall stress (r = -0.71, p less than 0.001). It is concluded that in patients with hypertension (1) left ventricular hypertrophy is correlated only modestly with measurements of resting blood pressure; and (2) the classic pattern of concentric left ventricular hypertrophy, as measured by relative wall thickness, is more closely related to the "typical" hypertensive abnormality of elevated peripheral resistance, suggesting that these anatomic and hemodynamic changes may be pathophysiologically interdependent. Furthermore, left ventricular performance declines when the pressure overload in hypertension is not offset by compensating hypertrophy, allowing wall stresses to increase.     

The contributions of sympathetic tone and the renin-angiotensin system to severe chronic congestive heart failure: Response to specific inhibitors (prazosin and captopril)

The contribution of sympathetic tone and the renin-angiotensin system to the pathogenesis of chronic heart failure was evaluated. In 20 paired studies of the same 10 patients, the baseline hemodynamic and humoral correlates of congestive heart failure, and the response to alpha adrenergic blockade (prazosin) and angiotensin converting enzyme inhibition (captopril) were assessed. Despite the extent of failure, baseline plasma renin activity ranged from normal to very high. In contrast, baseline plasma catecholamlne levels were always elevated. Baseline plasma norepinephrine reflected the severity of heart failure, correlating inversely with baseline cardiac index before administration of both drugs. Comparable improvement in left ventricular function was noted after acute therapy. Baseline renin and norepinephrine did not predict the response to prazosin, but baseline renin did predict the response to captopril: pulmonary wedge pressure (r = ?0.776, p < 0.01), stroke index (r = 0.752, p < 0.02), systemic vascular resistance (r = ?0.673, p < 0.05).In summary, elevated levels of plasma norepinephrine were inversely correlated with baseline cardiac function, but norepinephrine levels did not change despite improved hemodynamics with specific prazosin therapy. The renin-angiotensin system exhibited a wide spectrum of activity and hemodynamic improvement with captopril was related to this activity. Absence of a correlation between plasma norepinephrine and plasma renin activity suggested that their contributions to vasoconstriction were not interdependent. Increased sympathetic tone was consistent in severe heart failure, whereas renin-angiotensin activity differed widely. The response to captopril can be used to identify a subset of patients with severe heart failure and adverse angiotensin-mediated vasoconstriction.     

Nongeometric determination of right ventricular volumes from equilibrium blood pool scans

It has previously been shown that left ventricular volumes can be measured accurately from radionuclide gated blood pool scintigrams by quantttating the background-corrected and volume-normalized ventricular activity at end-diastole and end-systole. To determine if this same technique can be applied to the calculation of right ventricular volumes, simultaneous measurements of right ventricular stroke volume were performed using gated scintigraphy and the thermodilution technique in 60 patients without clinical or hemodynamic evidence of right-sided regurgitation. Three techniques for the acquisition of the radionuclide studies were evaluated. The best correlation between scintigraphic and thermodilution determinations of stroke volume was obtained for studies acquired with a 25 ° rotating slant hole collimator positioned in a 10 to 15 ° left anterior oblique projection with the collimator slant directed toward the cardiac apex along the axis of the interventricular septum: Thermodilution stroke volume = 4.2 (scintigraphic stroke volume) + 10.3 ml (correlation coefficient [r] = 0.88; standard error of the estimate = 9.3 ml; probability [p] < 0.0001). This scintigraphic acquisition technique was superior to (1) a straight bore collimator positioned in a septal projection (30 to 50 ° left anterior oblique with 15 ° caudal tilt), and (2) a 25 ° slant hole collimator positioned in a similar septal projection with the collimator slant directed caudally. This method was evaluated prospectively in an additional 14 patients, and there was excellent agreement between stroke volumes obtained with thermodilution and scintigraphic methods (r = 0.96, p < 0.001). In addition, measurements of right ventricular ejection fraction by the equilibrium method agreed closely with those obtained with a gated first pass technique (r = 0.94, p < 0.001, n = 14). With use of the scintigraphic right ventricular ejection fraction and the relation between scintigraphic and thermodilution measurements of right ventricular stroke volume, right ventricular end-diastolic and end-systolic volumes can be estimated. Thus, nongeometric radionuclide techniques may be used for the quantitation of right ventricular volumes.     

Improved exercise ejection fraction with long-term prazosin therapy in patients with heart failure

To study the effect of prazosin therapy on left ventricular function in patients with chronic stable heart failure, first pass radionuclide angiography at rest and during exercise was performed in 15 patients before the administration of prazosin and after seven to 12 weeks of prazosin therapy. There was no significant change in resting ejection fraction before and during prazosin therapy (36 ± 14 per cent versus 37 ± 14 per cent) (mean ± standard deviation). However, exercise ejection fraction increased from 34 ± 14 per cent to 42 ± 17 per cent (p < 0.01). The difference in ejection fraction from rest to exercise (ejection fraction response) changed significantly from ?2 ± 6 per cent before prazosin therapy to +5 ± 7 per cent during prazosin therapy (p < 0.01). Exercise duration increased from 368 ± 82 seconds to 476 ± 82 seconds (p < 0.01). Total work capacity measured in kilojoules increased from 12.6 ± 8.3 to 18.6 ± 10.4 (p < 0.01). The improved ejection fraction response during prazosin therapy correlated with the improved work capacity (r = 0.69, p < 0.01) and exercise duration (p = 0.59, p < 0.05). This improvement occurred despite a significant weight gain with prazosin from 72.2 ± 20.8 kg to 73.5 ± 20.8 kg (p < 0.01).These data suggest that long-term prazosin therapy is effective in the treatment of heart failure. However, the beneficial effects of prazosin, an alpha₁ blocking agent, may be evident only during exercise.     

Measurement of left ventricular ejection fraction in pediatric patients using the nuclear stethoscope

Left ventricular (LV) ejection fraction (EF) was measured in 25 patients, aged 2 weeks to 20 years (mean 8.6 years), using a portable nonimaging scintillation stethoscope. Technically satisfactory studies were obtained in 23 patients. LVEF was validated by cineangiography in 19 patients and by standard gated blood pool scintigraphy in 4. EF measured by the nuclear stethoscope correlated well with values obtained by cineangiography or scintigraphy (r = 0.869, p less than 0.001) over a wide range of EF values (18 to 79%). In children younger than 5 years (n = 11), the correlation (r = 0.728, p less than 0.02) was less satisfactory than in those older than 5 years (r = 0.926; p less than 0.001). Although modifications in the instrument and further clinical trials with the stethoscope are needed before the device becomes clinically useful to pediatric cardiologists, our data indicate that the nuclear stethoscope can provide reliable assessment of LVEF in pediatric patients.     

Quantification of valve regurgitation by radionuclide angiography before and after valve replacement surgery

Radionuclide gated cardiac blood pool imaging was used to quantify the severity of valve regurgitation in 20 patients, by calculating the ratio of left ventricular to right ventricular stroke counts (end-diastolic minus end-systolic counts in right and left ventricular regions of interest). This ratio (the stroke index ratio) was substantially higher in patients with aortic and mitral regurgitation (3.91 ± 1.45) than in a control group of 10 patients without regurgitation (1.32 ± 0.15), p < 3.001. The stroke index ratio correlated closely (r = 0.947) with measurements of regurgitant fraction derived from simultaneous determinations of total and forward stroke volumes during cardiac catheterization.After aortic and mitral valve replacement in 18 patients, the stroke index ratio decreased from 4.03 ± 1.46 to 1.38 ± 0.23 (p < 0.001), a value not significantly different from that observed in patients without regurgitation. All three patients with residual postoperative regurgitation had a stroke index ratio greater than 2 standard deviations above the mean values for the control group (>1.62), whereas the remaining 15 patients, who had no evidence of regurgitation, had values within the normal range. Therefore, radionuclide gated blood pool scanning provides a noninvasive method of quantifying valve regurgitation and assessing the results of medical or surgical interventions.     

Validation of the angiographic accuracy of digital left ventriculography

Digital subtraction angiography enhances the contrast to background signal, enabling the performance of angiography with reduced doses of contrast medium. The objectives of the present study were (1) to validate the accuracy of digital left ventriculography for measurement of left ventricular volumes and segmental contraction; and (2) to compare the hemodynamic effects resulting from low-and high-dose intraventricular contrast injections. Twenty-eight patients underwent digital left ventriculography, performed by intraventricular injection of 7 ml of contrast medium diluted in saline solution, followed by conventional cineangiography of the left ventricle performed with 45 ml of undiluted contrast medium. Left ventricular volumes calculated from digital ventriculograms correlated well with volumes calculated from conventional ventriculograms: end-diastolic volume (r = 0.97, standard error of estimate [SEE] 23.4 ml; end-systolic volume (r = 0.97, SEE 15.4 ml); stroke volume (r = 0.95, SEE 14.7 ml); and ejection fraction (r = 0.97, SEE 3.8%). Segmental left ventricular contraction, measured as percent chordal shortening of hemiaxes, correlated moderately well (r = 0.81, SEE 11.5%). After injection of undiluted contrast medium, left ventricular systolic pressure decreased (133 +/- 31 to 123.5 +/- 27 mm Hg; p less than 0.01) and left ventricular end-diastolic pressure increased (12.0 +/- 7 to 16.9 +/- 10 mm Hg; p less than 0.001). Left ventricular systolic and end-diastolic pressures did not change significantly after injection of diluted contrast medium, and patients had no discomfort. Thus, digital subtraction angiography permits the performance of left ventriculography with markedly reduced doses of contrast medium, obviating the hemodynamic effects resulting from injection of conventional doses of contrast medium. This new approach to left ventriculography provides high resolution ventriculograms for accurate measurement of left ventricular volumes, stroke volume, and ejection fraction.     

Duration of ejection in aortic stenosis: effect of stroke volume and pressure gradient

The theoretical effect of variable ventricular function on left ventricular ejection time in aortic stenosis was predicted by applying data measured in 52 patients with pure aortic stenosis to equations derived from the relations of Gorlin and Gorlin and Weissler et al. Ejection time and aortic valve area are not, of necessity, linearly related because (Formula: see text) where LVET is left ventricular ejection time, k is a constant, SV is stroke volume, PG is mean aortic pressure gradient and AVA is aortic valve area. When the patients were separated into performance groups on the basis of cardiac index (at 2.8 liters/min per m2), the linear regression relating the measured SV/square root PG with valve area in 18 patients with normal function (SV/square root PG = 11.1 AVA + 2.0, r = 0.969, p less than 0.001) predicted ejection time prolongation with decreasing valve area. In 34 patients with poor function, however, the decrease in SV/square root PG with decreasing valve area was more marked (SV/square root PG = 12.6 AVA + 0.4, r = 0.894, p less than 0.001), predicting a shorter ejection time at any given valve area in this group. As predicted by the effect of valve area on the equation, ejection time becomes most variable at a small aortic valve area. Independent ejection time measurement in these patients validated the predicted effect.     

Coronary hemodynamic effects of angiotensin inhibition by captopril and teprotide in patients with congestive heart failure

The coronary hemodynamic effects of vasodilator therapy with angiotensin-converting enzyme inhibitors (captopril arid teprotide) were studied in 11 patients with ischemic heart disease and severe congestive heart failure (CHF). Over 2 hours, systemic vascular resistance was reduced from 2,408 ± 240 to 1,715 ± 170 dynes·s·cm^?5 (p < 0.001), and cardiac output improved 18%, resulting in lower arterial pressure (101 ± 8 to 86 ± 5 mm Hg, p < 0.001) and left ventricular filling pressure (30 ± 2 to 21 ± 2 mm Hg, p < 0.001). Coronary sinus thermodilution blood flow parallelled perfusion pressure but did not significantly vary overall (160 ± 20 to 133 ± 12 ml/min, difference not significant [NS]). Coronary vascular resistance was unchanged. Although the left ventricular stroke work index rose slightly (37.7 ± 8.8 to 41.3 ± 7.9 g·m/m², p < 0.05), there was no change in the coronary arteriovenous oxygen content difference (10.8 ± 1.0 to 10.4 ± 1.0 ml/100 ml, NS) or calculated myocardial oxygen consumption (16.4 ±1.9 to 13.9 ± 1.6 ml/min, NS). The heart rate-systolic blood pressure product declined significantly during this period (8,824 ± 703 to 7,087 ± 514 beats·mm Hg, p < 0.02); this relief of cardiac effort was a function of the pretreatment plasma renin activity. A derived index of external myocardial efficiency improved 37% (19 ± 3 to 26 ± 6, p < 0.05), reflecting greater left ventricular work without increased oxygen demand.Enhancement of myocardial performance after converting enzyme inhibition appears dependent on reduction of angiotensin-mediated ventricular afterload and preload. The lack of coronary vasomotor effects in patients with advanced ischemic cardiomyopathy may reflect limited coronary vascular reserve. Improvement of heart failure in these patients developed without evidence of myocardial ischemia, since balance was maintained between oxygen supply and demand.     

Prevalence,characteristics and significance of ventricular tachycardia (three or more complexes) detected with ambulatory electrocardiographic recording in the late hospital phase of acute myocardial infarction

A 24 hour electrocardiographic recording was performed before hospital discharge in 430 patients who survived the cardiac care unit phase of acute myocardial infarction. Fifty patients (11.6 percent) had ventricular tachycardia, that is, three or more consecutive ventricular complexes. In 25 (50 percent) of these 50 patients, there was only one episode of ventricular tachycardia and, in 15 patients (30 percent), the longest run of ventricular tachycardia was only three consecutive ventricular premature depolarizations. The average rate of tachycardia was 119/min. Tachycardia rarely started with R on T ventricular premature complexes (4 of 1,370 episodes in 50 patients).There was no difference between the groups with and without ventricular tachycardia with respect to age and sex, but the patients with tachycardia had a significantly greater prevalence of previous myocardial infarction, left ventricular failure in the cardiac care unit, atrial fibrillation, ventricular tachycardia or ventricular fibrillation in the cardiac care unit and significantly more frequent use of digitalis and diuretic and antiarrhythmic drugs at the time of hospital discharge.The group with tachycardia had a 38.0 percent 1 year mortality rate compared with the rate of 11.6 percent in the group without tachycardia. Ventricular tachycardia had a strong association with 1 year mortality (odds ratio = 4.7). Although ventricular tachycardia had a significant association with many other postinfarction risk factors, it was still significantly associated with the 1 year mortality (p < 0.05) when other important risk variables were controlled statistically using a multiple logistic regression model. The 36 month cumulative mortality rate was 54.0 percent in the group with ventricular tachycardia compared with 19.4 percent in the group without tachycardia.     

Coronary flow studies in patients with left ventricular hypertrophy of the hypertensive type. Evidence for an impaired coronary vascular reserve

Increased myocardial blood flow occurs in ventricular hypertrophy, but flow per 100 grams of myocardium remains normal. The increase in flow may be obtained at the expense of the existing coronary vascular reserve or by an increase in the vascular bed. The coronary vascular reserve was studied by analyzing the hyperemic reaction to selective injection of contrast agent into the coronary arteries in 25 patients: a control group (9 patients) with chest pain syndrome, normal coronary arteries and a normal left ventricle (Group I) and 16 patients with aortic stenosis, left ventricular hypertrophy and normal coronary arteries (Group II). The hyperemic response in Groups I and II was 73.3 +/- 2.2 and 65.8 +/- 9.1 percent, respectively (difference not significant). Group II was subdivided into two groups: Group IIA had five patients with a left ventricular mass of less than 200 g (mean 158.8 +/- 25.9); this group had a hyperemic response of 102.3 +/- 9.9 percent. Group IIB had 11 patients with a left ventricular mass of more than 200 g (mean 308.9 +/- 22.5) and a hyperemic response of 49.27 +/- 10.42 percent. The hyperemic response was correlated with the diastolic left ventricular-aortic gradient (r = +0.64, p less than 0.001), left ventricular mass (r = -0.51, p less than 0.01) and aortic diastolic pressure (r = +0.636, p less than 0.001). Group I had a left ventricular mass similar to that of Group IIA (124.9 +/- 9 and 158.8 +/- 26 g, respectively) but a lower hyperemic response (73.3 +/- 2 and 102.3 +/- 10 percent, respectively). These data suggest that severe left ventricular hypertrophy is associated with a reduction in coronary vascular reserve; it is speculated that this decrease in the vascular reserve capacity may be related to the ischemic component of hypertrophic heart disease.     

Resting U wave inversion as a marker of stenosis of the left anterior descending coronary artery

Resting 12-lead electrocardiographic records from 849 patients who underwent coronary cineangiographic studies were reviewed for U wave negativity without knowledge of the clinical data or angiographic results. In order to evaluate U wave negativity as an independent electrocardiographic sign, patients with significant Q waves in the anterior leads were excluded from the final data analysis leaving 760 patients. Twenty-seven patients had U wave negativity in leads I, a VL or V₄ through V₆. For the study population, the prevalence of coronary artery disease was 64 percent (484 of 760); the prevalence of significant left anterior descending or left main coronary artery stenosis was 46 percent (350 of 760); and the prevalence of angiographic left ventricular dysfunction was 41 percent (309 of 754). Among 27 patients with resting U wave negativity the prevalence of coronary artery disease was 89 percent (24 of 27); the prevalence of left anterior descending or left main disease was 89 percent (24 of 27); and the prevalence of angiographic left ventricular dysfunction was 80 percent (20 of 25). Among patients selected for coronary cineangiographic study, U wave negativity was a significant predictor (p <0.001) of ?75 percent stenosis of the left anterior descending or left main coronary artery and of left ventricular dysfunction (p <0.001).     

Radionuclide evaluation of postextrasystolic potentiation of left ventricular function induced by atrial and ventricular stimulation

Postextrasystolic potentiation of left ventricular function induced by ventricular and atrial stimulation was compared in 10 patients using radionuclide ventriculography. After insertion of pacing wires, a preliminary radionuclide ventriculogram was obtained and then ventricular and atrial trigeminy was induced in random order, each with identical R-R coupling intervals, each for 6 to 10 minutes. During the stimulation studies, radionuclide data were acquired in electrocardiographic gated list mode format. Left ventricular ejection fraction and relative end-diastolic and end-systolic volume changes were measured for each reformatted composite sinus, atrial and ventricular premature beat and potentiated beat. The volume changes were normalized to the count-based values obtained for the sinus beat of the appropriate study. Postextrasystolic potentiation induced by either ventricular or atrial stimulation was characterized by similar significant increases in left ventricular ejection fraction (mean ± standard deviation 7 ± 3 percent, p < 0.01 versus 7 ± 5 percent, p < 0.01; difference not significant [NS]) and decreases in relative end-systolic volume (?12 ± 12 percent, p < 0.01 versus ?12 ± 8 percent, p < 0.01; NS) but little change in relative end-diastolic volume (+5 ± 10 percent, NS versus +4 ± 7 percent, NS; NS). This was despite a longer compensatory pause (1,120 ± 220 versus 1,050 ± 190 ms, p < 0.01) after the ventricular premature beat. It is concluded that there is no difference in the postextrasystolic potentiation induced by atrial or ventricular premature stimulation.     

Accuracy of left ventricular ejection fraction determined by the nuclear stethoscope

We assessed left ventricular ejection fraction 47 times in 21 patients with sinus rhythm by a portable non-imaging nuclear probe. After ^99mTc blood pool labelling, left ventricular ejection fraction was determined by probe in two different ways: on a beat-to-beat basis, and by the so-called ventricular function mode, based on the gated equilibrium principle, and subsequently compared with left ventricular ejection fraction measured by gated equilibrium radionuclide angiocardiography using a gamma camera.Left ventricular ejection fraction by probe correlated well with left ventricular ejection fraction by gamma camera: beat-to-beat versus gamma camera: r = 0.90, y = 0.75x + 0.12; ventricular function versus gamma camera: r = 0.88, y = 0.87x + 0.08. Also, left ventricular ejection fraction values determined by the two probe methods correlated closely: r = 0.97, y = 0.83x + 0.07. Compared with the gamma camera, the probe overestimated slightly the small values of left ventricular ejection fraction and underestimated high values. Correct determination of left ventricular ejection fraction by a non-imaging probe depends on correct positioning over the left ventricle and selection of a proper background activity level.The main application of this instrument is probably non-invasive bedside determination and monitoring of changes of left ventricular function occurring spontaneously or caused by cardiac arrhythmias or treatment with cardiac drugs.     

Effect of diuresis on the performance of the failing left ventricle in man

To determine the effect of diuresis on the performance of the failing left ventricle, we measured cardiac output, pulmonary wedge pressure and M-mode echo left ventricular diastolic dimension before and after diuresis in 13 patients with heart failure. Diuresis increased stroke volume (43 ± 23 ml to 50 ± 18 ml (p < 0.05) and decreased pulmonary wedge pressure (28 ± 3 mm Hg to 19 ± 5 mm Hg (p < 0.01)), mean blood pressure (100 ± 14 mm Hg to 88 ± 10 mm Hg (p < 0.01)) and systemic vascular resistance (2,059 ± 622 dynes-sec-cm^?5 to 1,783 ± 556 dynes-sec-cm^?5 (p < 0.05)). Echo left ventricular diastolic dimension was not changed by diuresis (6.0 ± 0.8 cm to 6.0 ± 0.8 cm). Percent change in stroke volume correlated with systemic vascular resistance (r = 0.60, p < 0.05) and with left ventricular diastolic dimension (r = 0.62, p < 0.05) but not with pulmonary wedge pressure (r = 0.12) or right atrial pressure (r = 0.04). Thus, diuresis improved the performance of the failing ventricle and reduced afterload, but it did not alter left ventricular diastolic dimension, an index of preload. These data suggest that diuresis improves ventricular function by decreasing afterload.