Heart rate variability and left ventricular dilatation early after myocardial infarction.

To assess clinically whether alterations of autonomic tone precede left ventricular dilatation, heart rate variability and early left ventricular dilatation after a first myocardial infarction were assessed. Low-frequency power (LF), high-frequency power (HF), and total power (TP) were obtained by ambulatory electrocardiogram on day 1 in 53 patients with a first acute myocardial infarction. Left ventricular end-diastolic volume determined by echocardiography was obtained on day 1 and day 14. Stepwise linear regression analysis was used to assess the associations of early left ventricular dilatation with heart rate variability adjusted for clinical variables. Higher LF and TP were significantly associated with early left ventricular dilatation after adjustment for age, sex, site of myocardial infarction, acute revasucularization, peak creatine kinase level, history of hypertension, and use of angiotensin-converting enzyme inhibitors and beta-blockers. Higher LF and TP preceded early left ventricular dilatation after myocardial infarction.

Resolution of late potentials with improvement in left ventricular systolic function in patients with first acute myocardial infarction.

BACKGROUND: Ventricular late potentials predict subsequent arrhythmic events and sudden death in postinfarction patients. Late potentials are recorded in the infarcted area, but it should be pointed out that they probably represent micropotentials in the area of delayed conduction found among isolated areas of scar tissue and normal myocardium. HYPOTHESIS: The study was undertaken to investigate the relationship between chronic reversible myocardial ischemia, such as stunned or hibernating myocardium, and late potentials in 38 patients with a first myocardial infarction. METHODS: The patients were divided into two groups, one with (Group 1) and one without (Group 2) resolution of late potentials recorded by signal-averaged electrocardiogram at 6 months after onset of myocardial infarction. We investigated the clinical, echocardiographic, and signal-averaged electrocardiographic characteristics of Groups 1 and 2. RESULTS: In the chronic phase of myocardial infarction, a higher incidence of patency of the infarct-related artery and an improvement of wall motion score were found in Group 1, and left ventricular ejection fraction was better preserved in Group 1 than in Group 2. CONCLUSIONS: These results suggest that the resolution of late potentials was influenced by the improvement of left ventricular systolic function and patency of the infarct-related artery. We concluded that chronic reversible myocardial ischemia, such as stunned or hibernating myocardium, might be the substrate that generated late potentials.

Left atrial function as a reliable predictor of exercise capacity in patients with recent myocardial infarction.

STUDY OBJECTIVE: To examine the relation between left atrial (LA) function and exercise performance. DESIGN AND SETTING: Retrospective study at a referral cardiopulmonary exercise laboratory in a university hospital. PATIENTS: Forty-one patients with recent myocardial infarction. INTERVENTIONS: M-mode echocardiography and cardiopulmonary exercise testing combined with radionuclide ventriculography. MEASUREMENTS AND RESULTS: Hemodynamic measurements were obtained at rest and peak exercise. LA fractional shortening at rest was used as an index of global LA function. LA fractional shortening had fair correlations with peak oxygen consumption (r=0.67, p<0.01) and exercise duration (r=0.71, p<0.01). Although there were no significant relations between LA fractional shortening and hemodynamic measurements at rest, LA fractional shortening was positively related to peak cardiac output (r=0.61, p<0.01) and peak stroke volume (r=0.57, p<0.01), and negatively related to peak pulmonary arterial wedge pressure (r=-0.44, p<0.05). In addition, LA fractional shortening correlated significantly with an increase in left ventricular (LV) end-diastolic volume from rest to peak exercise (r=0.48, p<0.02), but did not correlate with the changes in ejection fraction and end-systolic volume during exercise. An increase in LV end-diastolic volume during exercise was significantly related to peak oxygen consumption (r=0.46, p<0.02), peak cardiac output (r=0.60, p<0.01), and peak stroke volume (r=0.53, p<0.01), whereas the changes in ejection fraction and end-systolic volume during exercise were not related to these indexes. CONCLUSIONS: Exercise capacity and LV performance during exercise were mainly dependent on LV diastolic filling rather than systolic contraction during exercise. LA fractional shortening at rest reflected LV diastolic filling during exercise and, therefore, predicted cardiac output and stroke volume responses to exercise and exercise capacity in patients with recent myocardial infarction.

Prevalence, resolution, and determinants of late potentials in patients with unstable angina and left ventricular wall motion abnormalities.

Although transient myocardial ischemia such as exercise-induced ischemia has not been reported to be associated with the occurrence of late potentials, the association of late potentials with more profound ischemic damage, which is represented by reversible but prolonged left ventricular wall motion abnormalities, has not been demonstrated. We prospectively evaluated 37 unstable angina patients who had reversible but prolonged wall motion abnormalities after resolution of chest pain and electrocardiogram (ECG) changes. Signal-averaged ECG (SAECG) and echocardiogram were recorded during the acute phase and before hospital discharge. Late potentials were present in 6 (16 percent) patients on the initial SAECG recording and resolved in all 6 patients on the second recording before hospital discharge. Normalization of inferior left ventricular wall motion abnormality and multivessel disease were observed more frequently in patients with late potentials on the initial recording than in patients without (p < 0.05 and p < 0.05, respectively). In conclusion, late potentials were observed in patients who had reversible but prolonged wall motion abnormalities; these late potentials were resolved with improvement of left ventricular wall motion abnormalities. These results suggest that myocardial ischemia with prolonged wall motion abnormalities is a possible mechanism of the occurrence of late potentials.

PQ segment depression in acute Q wave inferior wall myocardial infarction.

BACKGROUND: PQ segment deviation is almost as characteristic as the classic ST segment deviation and is detected in most patients with pericarditis. However, as infarction-associated pericarditis remains over the infarct zone, PQ segment depression is observed much less often in patients with acute myocardial infarction. METHODS AND RESULTS: We designed this study to examine the clinical significance of PQ segment depression in acute Q wave inferior myocardial infarction. We examined 171 consecutive patients with acute Q wave inferior myocardial infarction by means of auscultation, ECG, and two-dimensional echocardiography. The diagnosis of pericarditis was made on the basis of pericardial rub detected by more than two observers during the first 3 days after admission. At least 0.5 mm of PQ segment depression from the TP segment lasting more than 24 hours in both limb and precordial leads was considered diagnostic of PQ segment depression. CONCLUSIONS: PQ segment depression was present in 14 patients and absent in 157 patients. Eleven patients with and 55 patients without PQ segment depression had advanced asynergy (akinesis or dyskinesis) in the posterior segments, whereas 9 patients with and 20 patients without PQ segment depression had pericardial rub. When multivariate analysis was performed to determine the important variables related to the occurrence of PQ segment depression, pericardial rub was selected with advanced asynergy of the posterior segment as significant factors related to PQ segment depression. Major complications (ventricular fibrillation, sustained ventricular tachycardia, cardiogenic shock, need for pacing) were present in 63 patients; 9 with (64%) and 54 without (34%) PQ segment depression. PQ segment depression was one of the clinical signs of more extensive damage extending to the posterior segments and increased incidence of major complications.

Clinical significance of pericardial effusion in Q-wave inferior wall acute myocardial infarction.

To assess the clinical significance of pericardial effusion in Q-wave inferior wall acute myocardial infarction, 185 consecutive patients were examined by means of electrocardiogram, echocardiogram and hemodynamic monitoring. A pericardial effusion was present in 44 patients and was absent in 141 patients. Electrocardiographic right ventricular infarction (> or = 1 mm of ST-segment elevation and Q wave in V4R) was detected in 54 patients, with 20 patients having pericardial effusion. Patients with pericardial effusion had significantly more left ventricular segments with advanced asynergy, lower cardiac output, higher pulmonary artery wedge pressure and higher incidence of right ventricular infarction than those without pericardial effusion. There were 17 in-hospital deaths. Although there was no significant difference in the mortality rate between patients with and without right ventricular infarction, a significantly higher hospital mortality rate was observed in patients with pericardial effusion compared to those without it (23 vs 5%). Pericardial effusion was selected with age and pulmonary artery wedge pressure as important variables associated with hospital mortality by the discriminant analysis. Patients who developed pericardial effusion, regardless of right ventricular infarction, had more extensive myocardial damage, and hence, pericardial effusion was one of the predictors of increased hospital mortality.

Effect of body characteristics on the variables of signal-averaged electrocardiograms in healthy subjects.

Late potentials have been reported to be affected by body size or left ventricular mass. To our knowledge, however, the effect of subadipose tissue, which is known to influence QRS amplitudes of the surface ECG on the variables of late potentials, has not been evaluated. The relationships between the variables of late potentials and various obesity indices were assessed in 45 men, aged 24 to 38 years, without structural heart disease and bundle branch blocks. QRS duration (DUR), root mean square voltage in the last 40 ms (RMS), and low-amplitude signals < 40 microV (LAS) were obtained by signal-averaged ECG. Left ventricular mass (LV mass) was determined by echocardiography. The DUR and RMS had no correlation with body height, weight, body mass index (BMI), sum of skin folds (triceps and subscapular), or LV mass. Positive linear correlations were found between LAS and weight (r = 0.48, p < 0.002), BMI (r = 0.54, p < 0.002), sum of skin folds (r = 0.57, p < 0.002), and percent BMI (r = 0.54, p < 0.002). Subadipose tissue may shift the onset of the 40-microV point of LAS to the left with a consequent prolongation of LAS by attenuation of the QRS complex. These data suggest that the use of LAS alone or as a combination in an obese population for the definition of positive late potentials is inappropriate.

Clinical significance of PQ segment depression in acute Q wave anterior wall myocardial infarction.

OBJECTIVES: This study was designed to evaluate the clinical significance of PQ segment depression and to examine the frequency of PQ segment depression in infarction-associated pericarditis. BACKGROUND: PQ segment deviation is almost as characteristic as the classic ST segment deviation and is detected in most patients with pericarditis. However, the incidence and clinical characteristics of PQ segment depression in acute myocardial infarction are not defined. METHODS: Three hundred four consecutive patients with acute Q wave anterior wall myocardial infarction were examined carefully by auscultation, electrocardiogram, echocardiogram and chest roentgenogram. The diagnosis of pericarditis was made on the basis of pericardial rub detected by more than two observers during the 1st 3 days after hospital admission. At least 0.5 mm of PQ segment depression from the TP segment observed for > 24 h in both limb and precordial leads was considered diagnostic of PQ segment depression. RESULTS: A pericardial rub was present in 65 patients (21%) and absent in 239 patients. PQ segment depression was detected in both limb and precordial leads in 30 patients (10%): 18 patients with pericardial rub and 12 patients without pericardial rub. On the basis of five clinical variables, multivariate analysis was performed to determine the important variables related to the occurrence of PQ segment depression. Pericardial rub was selected with left ventricular segments with advanced asynergy as a significant factor related to PQ segment depression. There were 31 in-hospital deaths, and a significantly higher hospital mortality rate was observed in patients with PQ segment depression (23% vs. 9%). CONCLUSIONS: Although PQ segment depression was observed in a minority of patients with infarction-associated pericarditis, it was one of the clinical signs of larger infarct size and increased hospital deaths.

Effect of ventriculoarterial coupling on residual left ventricular pump function in diabetic patients with myocardial infarction.

To study the ventriculoarterial coupling in diabetic patients with myocardial infarction (MI), 26 diabetic and 34 nondiabetic patients were investigated using radionuclide angiography in the 3rd week after acute MI. Effective arterial elastance was nearly one half of left ventricular end-systolic elastance in nondiabetic patients. On the other hand, effective arterial elastance was twice left ventricular end-systolic elastance in diabetic patients. These data suggest that a decrease in left ventricular contractility and an increase in effective arterial elastance lead to increased potential energy and decreased work efficiency in diabetic patients.

The factor dominating the determination of left ventricular filling varies during the first five days after acute myocardial infarction.

BACKGROUND: Left ventricular diastolic dysfunction may occur after the onset of acute myocardial infarction. Left ventricular diastolic filling dynamics are related to many factors. To evaluate the influence of left ventricular filling pressure on Doppler-derived left ventricular diastolic flow profiles in patients with acute myocardial infarction, we studied serial changes in filling during the first 5 days after the onset of uncomplicated acute myocardial infarction. METHODS: The study population consisted of 14 patients with acute myocardial infarction and 15 normal subjects: Doppler echocardiographic studies (left ventricular transmitral inflow and outflow velocity patterns) were performed on admission, and on the third and fifth days after infarction. Hemodynamic parameters were measured simultaneously using Doppler echocardiography. RESULTS: The E wave was lower, the A wave and A:E ratio were higher, deceleration half time and isometric relaxation time were prolonged, and peak left ventricular ejection flow velocity was lower in myocardial infarction patients than in normal subjects. The E wave and pulmonary capillary wedge pressure were positively correlated on the first and the third day (r = 0.77, P < 0.001, and r = 0.67, P < 0.01, respectively), but not on the fifth day. The E wave and isometric relaxation time were negatively correlated on the fifth day (r = -0.72, P < 0.01), but not on the first and third day. CONCLUSION: Left ventricular filling pressure (preload) was an important mechanism for maintaining left ventricular filling during the first 3 days, but the relaxation of the ventricle began to play a dominant role on the fifth day.

Effect of gender on the left ventricular diastolic performance during isometric handgrip exercise in normal individuals.

To evaluate the effects of gender and isometric handgrip exercise on left ventricular diastolic function in normal individuals, atrial and rapid filling fraction were investigated using M-mode echocardiography in 35 postmenopausal women and 31 age-matched men. There were no significant differences in heart rate, mean blood pressure, atrial filling fraction, and rapid filling fraction at rest between women and men. When the amount of change in hemodynamic variable during exercise was compared, there were no significant differences in heart rate and mean blood pressure between women and men. But the increase in atrial filling fraction and the decrease in rapid filling fraction were significantly larger in women than in men. These data suggest that left ventricular diastolic function is restricted in postmenopausal women, and left atrial booster pump action is mobilized when afterload is increased during isometric handgrip exercise.

Difference between women and men in left ventricular pump function during predischarge exercise test after acute myocardial infarction.

To evaluate the difference in left ventricular (LV) pump function during predischarge exercise testing between postmenopausal women and age-matched men with myocardial infarction, global and regional ejection fraction, LV end-diastolic volume, and the ratio of systolic blood pressure to LV end-systolic volume were investigated using radionuclide angiography in 25 postmenopausal women and 37 age-matched men. There were no significant differences in the resting radionuclide angiographic indexes between women and men. Global and regional ejection fraction of noninfarcted area, and the ratio of systolic blood pressure to LV end-systolic volume decreased at peak exercise in women, but these indexes increased in men. Although there was no significant difference in the amount of change in LV end-diastolic volume during exercise between the 2 groups, the amount of increase in LV end-systolic volume was significantly larger in women than in men. The ratio of systolic blood pressure to LV end-systolic volume had a curvilinear relation with LV end-diastolic volume at rest and peak exercise, but the ratio of systolic blood pressure to LV end-systolic volume was larger at any LV end-diastolic volume in men than in women during exercise. Thus, lower global ejection fraction and the ratio of systolic blood pressure to LV end-systolic volume during exercise in postmenopausal women compared with age-matched men indicate that gender may have played an important role in the LV remodeling process.

Disturbance of pulmonary gas exchange in patients with acute myocardial infarction-associated pericardial effusion.

To elucidate the effect of pericardial effusion on pulmonary gas exchange in patients with infarction-associated pericardial effusion, 294 consecutive patients with their first Q-wave anterior wall acute myocardial infarction were examined carefully by echocardiography, chest radiography and hemodynamic monitoring. A pericardial effusion was detected in 77 patients and was absent in 217 (group 1). Of the 77 patients with pericardial effusion, it was mild in 57 (group 2) and moderate in 20 (group 3). Patients with pericardial effusion (groups 2 and 3) had significantly greater pulmonary artery wedge pressure and more left ventricular segments with advanced asynergy than did those in group 1. Although there were no significant differences in pulmonary artery wedge pressure and number of left ventricular segments with advanced asynergy between groups 2 and 3, group 3 had significantly greater right atrial pressure, alveolar arterial oxygen difference and incidence of high radiographic score. Thus, accumulation of pericardial effusion to a moderate amount may contribute to the greater incidence of increase in extravascular lung water, and disturbance of pulmonary gas exchange.

Left ventricular diastolic filling properties in diabetic patients during isometric exercise.

Left ventricular diastolic filling properties during isometric handgrip exercise were measured by pulsed Doppler echocardiography in 33 noninsulin-dependent diabetic patients with a normal ejection fraction and 15 control subjects. Diabetic patients were subdivided into two groups according to their resting left ventricular filling pattern (A/E): 18 patients were in group DM-1 (A/E < or = 1.1) and 15 patients were in group DM-2 (A/E > 1.1). At rest, A/E ratio and A wave were higher, and deceleration half-time was longer in group DM-2 than in normal subjects and group DM-1, but there was no significant difference between normal subjects and group DM-1. The A/E ratio increased significantly in all three groups during isometric handgrip exercise. However, the change in A/E from rest to peak exercise in group DM-1 (0.29 +/- 0.20) was significantly greater than in normal subjects (0.09 +/- 0.07). These results suggest that diabetes mellitus patients with normal resting left ventricular (LV) filling pattern (group DM-1) had LV diastolic filling abnormalities with isometric handgrip exercise. Doppler echocardiography with isometric handgrip exercise is useful in identifying underlying left ventricular diastolic dysfunction in diabetic patients.

Ventriculoarterial coupling during low-level exercise testing after myocardial infarction.

To evaluate the change of ventriculoarterial coupling during low-level exercise in patients after myocardial infarction, the ratio of systolic blood pressure to left ventricular end-systolic volume (P/V ratio) and the ratio of systolic blood pressure to stroke volume (effective arterial elastance) were investigated using radionuclide angiography in 73 consecutive patients with a negative predischarge exercise test. The patients were divided into three groups according to their resting left ventricular ejection fraction: group A (n = 12) > or = 60%; group B (n = 32) 41-59%; group C (n = 29) < or = 40%. The ejection fraction increased significantly during exercise in all three groups. There was no significant difference in the change of the P/V ratio during exercise between groups A and B, but it was significantly smaller in group C. The effective arterial elastance increased during exercise in group A, did not change in group B, and decreased in group C. Thus, the augmentation of myocardial contractility was an important factor related to the increase in ejection fraction during exercise in patients with normal or slightly reduced cardiac function, whereas the decrease in effective arterial elastance was important in patients with poor cardiac function.

Residual left ventricular pump function after acute myocardial infarction in NIDDM patients.

OBJECTIVE: Left ventricular remodeling occurs immediately after MI, involving structural changes in noninfarcted segment. However, the residual left ventricular pump function in NIDDM patients after acute MI has not been clarified. The purpose of this study was to evaluate the difference in the process of left ventricular remodeling between NIDDM and nondiabetic patients. RESEARCH DESIGN AND METHODS: Left ventricular regional EF images obtained by radionuclide angiography were investigated in 20 NIDDM and 29 nondiabetic patients the 3rd wk after acute MI. RESULTS: Regional EF of the noninfarcted area and P/V had a significant hyperbolic relation with left ventricular EDV in both groups of patients. Despite no difference in the extent of myocardial necrosis and the number of coronary vessels diseased between NIDDM and nondiabetic patients, regional EF of the noninfarcted area and P/V were significantly lower when left ventricular EDV increased in NIDDM patients compared with nondiabetic patients. CONCLUSIONS: Pathogenetic changes of the residual myocardium associated with NIDDM may adversely influence the process of left ventricular remodeling after MI, especially in patients with increased left ventricular EDV.

Difference in the residual left ventricular pump function between anterior and inferior myocardial infarctions.

To evaluate the left ventricular regional ejection fraction (EF) of noninfarcted area in relation to the left ventricular end-diastolic volume (EDV) in patients with recent myocardial infarction (MI), 75 patients with Q-wave MI (anterior: 51 patients; inferior; 24 patients) were studied. The regional EF of noninfarcted area was obtained by radionuclide angiocardiography 4 weeks after the onset of MI and was used to estimate the left ventricular regional function of the noninfarcted area. Peak creatine kinase and QRS scores were not significantly different between anterior and inferior MI in each left ventricular EDV (EDV < or = 100, 101-139 and > or = 140 ml). Global EF and regional EF of noninfarcted area in anterior MI with left ventricular EDV > or = 140 ml was significantly lower than in those with EDV < or = 139 ml (p < 0.01), whereas there were no significant differences in global EF and regional EF of noninfarcted area in the three groups of left ventricular EDV in inferior MI. Thus, the effect of left ventricular EDV on regional EF of noninfarcted area and on the total cardiac performance was more important in anterior than in inferior MI, because a similar degree of left ventricular dilatation resulted in more severe derangements after anterior MI.

Diastolic time in diabetes. Impairment of diastolic time during dynamic exercise in type 2 diabetes with retinopathy.

To evaluate the effect of microangiopathic complications and autonomic dysfunction on diastolic time (DT) during dynamic exercise, 19 patients with type 2 diabetes and ten normal subjects were studied using ear densitography. All subjects had neither an ischemic electrocardiographic response nor chest pain during maximal treadmill exercise. The DT and heart rate (HR) had an inverse nonlinear relation, and electromechanical systole (QS2) and HR had an inverse linear relation during exercise. When the exercise DT-HR and QS2-HR relations were compared, a significant lengthening of QS2, with a consequent shortening of DT, was observed in diabetic patients with retinopathy, compared to patients without retinopathy and normal subjects (p less than 0.005), while no significant differences were found between diabetic patients without retinopathy and normal subjects; however, there were no significant differences in the exercise DT-HR and QS2-HR relations among diabetic patients with and without autonomic dysfunction and normal subjects. A more prominent abbreviation in the diastolic perfusion time observed in patients with retinopathy would be meaningful because microangiopathy might already have limited subendocardial blood flow. Thus, patients with type 2 diabetes who have retinopathy have a potential risk of aggravation of left ventricular function through the deterioration of myocardial blood flow.

Mixed venous oxygen saturation as a guide to tissue oxygenation and prognosis in patients with acute myocardial infarction.

The relation of mixed venous oxygen saturation and the cardiac index to tissue oxygenation and prognosis was investigated in 119 patients with acute myocardial infarction. There was a positive correlation between mixed venous oxygen saturation and the cardiac index in 97 survivors and 22 nonsurvivors, but a significantly lower mixed venous oxygen saturation level at the same level of cardiac index was observed in nonsurvivors compared with survivors. Results of multivariate analysis with mixed venous oxygen saturation and the cardiac index indicated that only mixed venous oxygen saturation was significantly related to survival and to hyperlactacidemia. Oxygen delivery to tissues declined significantly in nonsurvivors because of a lower cardiac index and a lower hemoglobin concentration in these patients than in survivors. However, at the same level of oxygen delivery to tissues, nonsurvivors had a significantly higher rate of oxygen consumption leading to a correspondingly greater decrease in mixed venous oxygen saturation, suggesting that a greater increase in oxygen demand was also observed in nonsurvivors than in survivors. Thus mixed venous oxygen saturation after acute myocardial infarction is a better predictor of hyperlactacidemia and survival than the cardiac index, and this may be associated with an increased oxygen demand and an impaired oxygen transport system in seriously ill patients.

Clinical significance of pericardial rub with regional ventricular dilatation.

To elucidate the clinical characteristics associated with regional ventricular dilatation in the early phase of myocardial infarction (MI), 228 patients with acute Q-wave anterior MI were studied. Forty-nine patients (21 percent) had echocardiographically demonstrated regional ventricular dilatation (an abnormal bulge in the left ventricular contour during both systole and diastole) on the third hospital day. Careful auscultation revealed that a pericardial rub was present in 49 patients (21 patients with and 28 patients without regional ventricular dilatation) during the first three days after hospital admission. Multivariate analysis was performed to determine the relative importance of pericardial rub with six other clinical variables related to regional ventricular dilatation. Pericardial rub and cardiac output were the significant factors related to the presence of regional ventricular dilatation. Thus, a pericardial rub, in concert with impaired left ventricular function, is a physical sign associated with regional ventricular dilatation, and anatomically transmural infarction is the possible factor explaining their association.