Evaluation of myocardial contractility in man

Relative tachycardia in ambulant children with borderline hypertension

Borderline hypertensives who demonstrate tachycardia have a tendency toward the development of essential hypertension. However, the documentation of tachycardia in previous studies has been generally based on brief periods of observation. In the present study, we measured heart rates through a 24-hour period in 16 ambulatory mildly hypertensive subjects (ages 5 to 23 years). When compared with normal matched controls, significantly (p less than 0.05) higher heart rates were observed during the waking periods (99 +/- 9 vs 90 +/- 11) and sleep periods (72 +/- 12 vs 62 +/- 7). Similar observations were also made for 24 hours (90 +/- 8 vs 79 +/- 8). In addition, hypertensives also demonstrated thickened (during diastole) left ventricular posterior wall (0.96 +/- 0.17 vs 0.85 +/- 0.13 cm; p less than 0.05) and interventricular septum (0.98 +/- 0.17 vs 0.84 +/- 0.19 cm; p less than 0.05). It is suggested that tachycardia may be an early manifestation of borderline hypertension in children.

Blood pressure related echocardiographic changes in adolescents and young adults

In 1973, standardized blood pressure measurements were obtained in 837 high school students in Bourbon County, Kentucky, a rural county with a high prevalence of individuals with systemic hypertension. In 1978, follow-up measurements of blood pressure were performed in selected individuals who were in the high, intermediate, and low ranges of the initial sex-specific blood pressure distributions. Relative rank order of initial blood pressure measurements over the five-year period was maintained. The results of this population-based study provided an opportunity to evaluate the cardiac status in young adults with relatively high blood pressures maintained over five years. Standard m-mode echocardiographic examinations were, therefore, performed over five years. Standard m-mode echocardiographic examinations were, therefore, performed at the time of follow-up. In individuals in the low and intermediate ranges for systolic blood pressure, indices of ventricular hypertrophy were directly correlated with blood pressure level. Among individuals with higher values for systolic blood pressure, after adjusting for the effects of relative body size, indices of ventricular hypertrophy were not significantly different from those noted in the intermediate group. Indices of cardiac performance and estimated left ventricular systolic wall stress were, however, significantly elevated in this "high" blood pressure group. Early in the course of systemic hypertension increased wall stress, rather than hypertrophy, appears to be the primary cardiac manifestation of elevated systolic blood pressure.

AR-L 115 in coronary artery disease: positive inotropic effects and increase of left-ventricular pump function without inducing angina

1. AR-L 115 improves pump function in patients with advanced and fully treated congestive cardiomyopathy. Since, in spite of such beneficial responses, the energy cost involved might be detrimental when used in advanced coronary artery disease, we monitored clinical haemodynamic and ECG responses to AR-L 115 (2 mg/kg body weight, bolus) in ten patients with coronary artery disease who had developed angina pectoris and/or pathological increases in left ventricular-end diastolic pressure (LVEDP) at the end of a 1 min pacing stress test. 2. When subjected to these stress conditions again (but this time during the peak effect of AR-L 115), there was no longer evidence of ischaemic myocardial impairment, neither clinically by ECG or haemodynamically. 3. There were (average) increase of 43% in cardiac index, 16% in heart rate, 27% in stroke index, 20% in ejection fraction, 31% in VCF and 39% in dp/dt max, while LVEDP decreased to normal values as if at resting conditions. All changes were significant (P less than 0.05). 4. LV-systolic pressure and end diastolic volume (P greater than 0.05) remained the same. Thus the AR-L 115-induced improved LV-pump function was accomplished under stress conditions in the absence of evidence for myocardial ischaemia.

Echocardiographic evaluation of fixed left ventricular outlet obstruction in children. Pre and postoperative outlet obstruction in children

Rencently, several investigators have utilized the echographically determined magnitude of relative left ventricular posterior wall hypertrophy as a reflection of normalized systolic wall stress to estimate left ventricular systolic pressure noninvasively. In this study, relative wall thickness determined echographically was compared to peak systolic pressure measured at catheterization in 20 children without obstruction to left ventricular outflow and with normal left ventricular function. From these data a relationship, pressure = 225 X left ventricular systolic wall thickness/left ventricular end-systolic internal dimension, was derived. The relationship was then applied to 57 children with fixed aortic stenosis. Left ventricular pressure estimated echographically compared well with that demonstrated at cardiac catheterization (r = 0.89). Twenty-one patients had further echographic studies following surgical relief of outlet obstruction. Estimated left ventricular pressure fell to normal values within two months following surgery in over half the patients with good surgical relief of obstruction, and was normal at subsequent studies up to 22 months postoperatively in all but one patient with good surgical relief. In patients in whom outlet obstruction was not adequately relieved at surgery, echographically estimated left ventricular pressure remained persistently elevated.

Abnormal regional metabolism and mechanical function in patients with ischemic heart diseases: improvement after successful regional revascularization by aortocoronary bypass

Left ventricular anterior wall metabolism was investigated concurrently with global myocardail metabolism by simultaneous preoperation sampling of anterior interventricular venous (AIV) and coronary sinus (CS) as well as arterial bloods in seven patients with severe obstructive lesions of the major coronary arteries, including left anterior descending. Postoperative study was performed two weeks to six months following successful aortocoronary artery bypass surgery. All grafts including the aorto-left anterior descending artery grafts were patent. Preoperatively in three of the seven patients, anterior wall lactate extraction (R%L) was negative at rest. The average R%L at rest (7 +/- 14%) was abnormal and was negative (-49 +/- 26%) at a maximum supraventricular pacing rate (MPR) of 137 +/- 4.6 beats/min. Postoperatively, not only was resting R%L (39 +/- 4;4%) normal but also it remained normal during atrial pacing (32 +/- 8.5%) even though the postoperative MPR (164 +/- 4.4 beats/min) was much higher than the preoperative MPR; Postoperatively AIV pO2 both at rest (21 +/- 1.1 mm Hg) and at MPR (22 +/- 1.3 mm Hg) and directly determined O2 saturations (resting: 34 +/- 3.0%; MPR:35 +/- 2.1%) tended to be higher than the preoperative values (AIV pO2, resting: 18 +/- 1.7; MPR: 19 +/- 1.7 mm Hg; AIV O2 saturation resting: 30 +/- 2.7; MPR: 33 +/- 3.3%), although only differences in pO2 were statistically significant. In five of the seven patients in whom the pre and postoperative left ventricular angiograms could be compared, systolic wall motion of the left ventricular anterior wall improved markedly postoperatively. Average global myocardial lactate extraction (G%L) preoperatively was normal (19 +/- 4.8%) at rest but was negative (-22 +/- 12%) at MPR. Postoperatively however, G%L both at rest (44 +/- 5.5%) and at MPR (34 +/- 7.9%) were normal. Coronary sinus pO2 and O2 saturation were also higher postoperatively compared to the preoperative values. Over-all left ventricular performance indicated by increase in ejection fraction also improved postoperatively. This improvement was not caused by increased coronary blood flow. Postoperative coronary sinus blood flow both at rest (114 +/- 19 ml/min) and at MPR (199 +/- 27 ml/min) however were less than the preoperative values (resting 136 +/- 24, MPR 261 +/- 40 ml/min), There was also no increase in global O2 delivery and O2 consumption despite higher heart rate and rate-pressure product achieved during postoperative pacing stress and the patients did not develop angina. These findings suggest that improved regional and global metabolism and mechanical functions observed postoperatively in these patients may be due to redistribution of blood flow to the ischemic and nonischemic myocardium following successful aortocoronary artery bypass surgery.

Beneficial effects of vasodilator agents in severe mitral regurgitation due to dysfunction of subvalvar apparatus

To assess the potential beneficial effects of vasodilator agents in patients with severe mitral regurgitation, sodium nitroprusside was administered intravenously at a rate of 16 to 100 µg/min in eight patients with clinically significant mitral regurgitation presumably due to dysfunction of the subvalvar apparatus. In all patients there was a decrease in the magnitude of the peak `V' wave (from 50 ± 4.5 to 19 ± 2.9 mm Hg) and in left ventricular filling pressure (33 ± 1.8 to 16 ± 1.4 mm Hg), together with a decreased intensity of the apical pansystolic murmur. There was a significant increase in forward cardiac index (2.2 ± 3.5 to 3.3 ± .47 liter/min/M 2 ) and forward stroke volume index (23 ± 4.4 to 36 ± 6.6 ml/M 2 ) along with a reduction in systemic vascular resistance (1802 ± 331 to 1102 ± 241 dynes/sec/cm -5 ). In the five patients in whom the therapy was continued, relief of symptoms of pulmonary venous congestion occurred. In the four patients in whom left ventricular volumes were determined angiographically, the observed increase in forward stroke volume was due to a reduction in the regurgitant fraction. These findings suggest that the use of vasodilator agents like nitroprusside can achieve the major objectives of treatment of patients with mitral regurgitation: an increase in forward stroke output, a reduction in regurgitant volume and a decrease in pulmonary venous pressure.

Influence of direct myocardial revascularization on left ventricular asynergy and function in patients with coronary heart disease. With and without previous myocardial infarction

The influence of successful aortocoronary artery bypass surgery on left ventricular asynergy and dysfunction was studied by hemodynamic and angiographic methods in 29 patients with coronary artery disease. Eight patients had the preinfarction syndrome, 10 patients had chronic ischemia without previous infarction, and 11 patients had chronic ischemia with previous infarction. LV asynergy was present preoperatively in 12 of the 18 patients in the first two groups. Marked improvement occurred in all and a normal wall motion was restored in the majority following surgery. More pronounced improvement was noted in the preinfarction syndrome as compared to the group with chronic ischemia and no previous infarct. The ejection fraction was reduced in 12 of the 18 patients in these two groups and significant improvement was observed postoperatively [0.45 ± 0.03 ( sem ) to 0.74 ± 0.03]. Increase in ejection fraction was primarily due to a decrease in the end-systolic volume (71 ± 12 to 23 ± 4 ml/m 2 ). The end-diastolic volume was only slightly reduced (114 ± 12 to 97 ± 9 ml/m 2 ). Left ventricular end-diastolic pressure fell from 15 ± 1 to 10 ± 1 mm Hg.

In nine of 11 patients who had previous myocardial infarction, abnormal wall motion was present preoperatively. Following surgery, some abnormalities of wall motion persisted in the areas of known infarction, although significant improvement of wall motion occurred in the noninfarcted segments. The ejection fraction was reduced in seven of these 11 patients and improved postoperatively. (0.44 ± 0.05 to 0.59 ± 0.05). The end-systolic volume decreased from 57 ± 5 to 41 ± 6 ml/m 2 , and the end-diastolic volume was unchanged (106 ± 5 to 108 ml/m 2 ). Left ventricular end-diastolic pressure fell from a mean value of 17 ± 3 to a mean value of 10 ± 2 mmHg following successful surgery. These findings are consistent with improved pump function and were associated with improvement in indices of contractile state. The observations indicate that significant improvement in ventricular wall motion and pump function occurs in patients with obstructive coronary disease following successful aortocoronary artery bypass surgery even in the presence of old myocardial infarction. Since the patients of the present study all had normal initial end-diastolic volumes, however, similar beneficial results might not occur in patients with cardiomegaly and more severe heart failure.