Changes In Systolic Time Intervals Research Articles

Effects of postextrasystolic potentiation on systolic time intervals

The changes in systolic time intervals associated with postextrasystolic potentiation were studied in 48 patients whose left ventricular function was categorized angiographlcally into four groups—normal function (I) and mlld (II), moderate (III) and severe (IV) left ventricular dysfunction. Postectopic potentiation in all groups caused a decrease in preejection period/left ventricular ejection time (PEP/LVET) ratio. The greatest potentiation and decreases in PEP/LVET ratio were noted in beats where the difference in compensatory pause and coupling interval (both expressed as percent of basic cycle length [CP percent — CI percent]) exceeded 40. The decrease in the ratio was least in the normal subjects (Group I) and maximal in Group IV patients. The pattern of response of the rate-corrected left ventricular ejection time and preejectlon period was also different at the four levels of ventricular function. Marked shortening of ejection time with minimal shortening of preejection period occurred in Group I, but in Group IV patients there was marked shortening of preejection period and minimal shortening of ejection time. An intermediate response was seen in Group II and III patients. The amount of shortening of ejection time exceeded that of preejection period in Group II patients; the reverse was true in Group III patients. The group responses differed with a significance of 2 P <0.001 except when Group II was compared with Group III, when the significance was 2 P <0.025. Thus, measurement of changes in systolic time intervals associated with postextrasystolic potentiation is of value as a noninvasive means of assessing resting left ventricular function.

Effects of precurarization on the heart measured by systolic time intervals.

The effects of precurarization, with or without prior atropine medication, on heart rate, systolic time intervals (preejection period (PEP) and left ventricular ejection time (LVET)) and derivatives from these were studied in 80 healthy patients before minor surgery. Atropine (0.5-0.7 mg i.v.) exerted a vagolytic action with no changes in systolic time intervals. D-tubocurarine (0.5 mg/kg b.w.) did not affect heart rate or systolic time intervals. Both gallamine (0.3 mg/kg b.w.) and pancuronium (0.015 mg/kg b.w.) increased heart rate due to the inherent vagolytic effect. Furthermore, a short-lasting decrease in PEP and an increase in LVET were demonstrated. Consequently, a fall in PEP/LVET and a rise in 1/PEP2 were induced, indicating an increase in cardiac pump performance. These changes were blocked by prior atropine medication, a result which is not easily explainable. Possible clinical implications are discussed.

The effect of near-maximal isometric stress on the presence and amplitude of fourth heart sounds

Near-maximal isometric exercise (IHG) was employed to provoke new, or alter pre-existing fourth heart sounds (S4s) in ambulatory middle-aged normal subjects (N), hypertensive patients (HHD), and patients with coronary disease (CAD). S4 amplitudes and systolic time intervals (STIs) were measured blindly. No subjects without a resting S4 developed a new S4 during IHG. Increases and decreases of pre-existing S4 provoked by IHG were not statistically different among all groups. Among subjects matched for presence of S4, STIs during IHG showed significant shortening of the ejection time index and prolongation of Q-Im in the HHD group only. When the subjects who increased a resting S4 during IHG were compared with the subjects who decreased their resting S4 during IHG there were no significant differences in the responses of STIs. Thus, in these ambulatory, hypertensive patients, coronary patients, and normal subjects, near-maximal IHG did not induce new S4s and had variable effects on pre-existing S4s. Neither type of S4-response could be associated with corresponding changes in systolic time intervals.

Systolic Time Intervals before and after Maximal Exercise Treadmill Testing for Evaluation of Chest Pain

The change in systolic time intervals from before exercise to three to four minutes following a maximal-exercise treadmill test was measured to eveluate chest pain in 110 fasting supine subjects. Forty-six (85 percent) of 54 patients with chest pain and with abnormal findings on coronary arteriograms were found to have at least a 10-msec prolongation in the left ventricular ejection time index (LVETI), whereas only two (8 percent) of 25 subjects without heart disease and 5 (16 percent) of 31 subjects with chest pain but with normal findings on coronary arteriograms had 10 msec or more of prolongation of the LVETI after exercise. The change in the other systolic time intervals (total electromechanical systole, preejection phase [PEP], and PEP/LVET) were less reliable in detecting the presence or absence of coronary disease. We conclude that determination of LVETI before and after maximal-exercise treadmill testing is a clinically useful noninvasive disgnostic test for obstructive coronary disease in patients with chest pain.

Changes in systolic time intervals during treatment of diabetes mellitus.

The cardiovascular response to the control of diabetes by sulphonylurea drugs has been investigated using systolic time intervals in a group of 19 diabetics. Before treatment a significantly greater heart rate and shortening of QS2 interval and left ventricular ejection time index were encountered among the more hyperglycaemic diabetic patients requiring drug therapy while all diabetics had a reduction of pre-ejection period index. There was a gradual return of resting heart rate and systolic time intervals to control values along with the fall in plasma sugar concentration during treatment. A likely explanation of the findings is that uncontrolled diabetics, particularly those more severely affected, are subjected to an increased adrenergic stimulus to the cardiovascular system which disappears with therapy. There is no evidence of positive inotropic action of sulphonylurea drugs in this study.

Negative Inotropic Effect of Lidocaine in Patients with Coronary Arterial Disease and Normal Subjects

The effect of administration of lidocaine on left ventricular performance was studied using systolic time intervals in nine normal subjects, eight patients with stable angina, and 15 patients with acute myocardial infarction. The greatest response in systolic time intervals occurred at three minutes after intravenous injection of lidocaine (100 mg), with values returning to baseline at 10 to 15 minutes. Administration of lidocaine produced a significant prolongation of the preejection period (PEP) corrected for heart rate in all groups and a prolongation of the ratio of PEP to left ventricular ejection time (PEP/LVET) in patients with angina. The group with acute myocardial infarction exhibited a hyperadrenergic state, as shown by a short baseline QS2I. The QS I was lengthened by administration of lidocaine in all groups, but this was more profound in those with acute myocardial infarction. These changes in systolic time intervals were still present at two hours after injection in six patients with acute myocardial infarction in whom an infusion of lidocaine followed the initial bolus. The effect of administering lidocaine after intravenous injection of propranolol (5 mg) was also studied in six normal subjects. Although propranolol therapy along prolonged the PEP/LVET, a further significant prolongation followed subsequent injection of lidocaine.

Use of noninvasive methods in evaluation of left ventricular performance in coronary artery disease. II: Change in systolic time intervals after coronary artery bypass in patients with stable angina.

Serial recording of systolic time intervals (STI) was used to assess changes in left ventricular (LV) function in 92 patients with stable angina undergoing coronary angiography and LV cineangiography. On the basis of angiography, patients were placed in the following study groups: mild or absent coronary artery disease group -21 patients with less than 70 per cent occlusion of all coronary arteries, considered to have non-significant coronary artery disease and not needing bypass surgery; surgical bypass group-52 patients with evidence of significant (less than 70%) obstruction of at least one coronary artery who underwent myocardial revascularization; and medical group-19 patients with evidence of significant coronary artery disease not undergoing bypass surgery. Measured STI, corrected for heart rate and sex, were expressed as indices. No significant differences were noted in the mean STI from the time of initial evaluation to second evaluation 3 to 6 months later in either the mold or absent coronary artery disease patients or the medical group. In the surgical bypass group, however, serial studies at initial angiographic evaulation and 3 to 6 months after bypass surgery showed a shortened pre-ejection period (PEP) from 150 +/- 20 to 142 +/- 16 mn (P less than 0-001), prolonged left ventricular ejection time (LVET) from 396 +/- 21 to 409 +/- 14 ms (P less than 0-02), and decreased PEP/LVET from 0-45 +/- 0-11 to 0-04 +/- 0-07 (P less than 0-02). Paired data analysis of the three groups also showed a significant change only within the surgical bypass group from initial to find study, with a shortened PEP (P less than 0-002), prolonged LVET (P less than 0-001), and decreased PEP/LVET (P less than 0-001). These data suggest improvement in LV function in patients with significant coronary artery disease within a few months of myocardial revascularization, without demonstrable change in STI in those patients with coronary artery disease not subjected to revascularization.

Left ventricular function after aortic valve replacement.

Changes in haemodynamics and in systolic time intervals, early after valve replacement, were studied in a group of 15 patients. Though all the haemodynamic measurements were within normal limits at 44 hours after operation, there was a persistent change in systolic time intervals (shortening of left ventricular ejection time and electromechanical systole, and prolongation of pre-ejection period and increase in the ratio PEP/LVET). The effect of periods of myocardial ischaemia during cardiopulmonary bypass on myocardial function is suggested as the explanation for the changes observed.

Cardiovascular effects of Althesin. Changes in systolic time intervals and peripheral tissue blood flow.

Systolic time intervals were studied and peripheral blood flow measurements made in twelve healthy patients before and after intravenous induction of anaesthesia with Althesin 0.05 ml per kg. The changes in systolic time intervals observed were considered to reflect the cardio-depressive properties of the drug. The reduction in peripheral blood flow which occurs in Althesin anaesthesia was confirmed. Measurement of systolic time intervals and peripheral blood flow constitute a simple and sensitive method for the evaluation of the effects of drugs on the cardiovascular system.

Changes in Systolic Time Intervals During Stepwise Increasing Hypoxia

Determinations of the reciprocal value of the square of the pre-ejection period (1/PEP-2) and the pre-ejection period/left ventricular ejection time-ratio (PEP/LVET-ratio) during stepwise increasing hypoxia showed in seven mongrel dogs in a decrease in PEP/LVET-ratio and an increase in 1/PEP-2 as an expression of a stimulation of the cardiac function. Significant changes were not observed before the arterial oxygen tension (Pao2) was below 40 mmHg. During severe hypoxia (Pao2 15-20 mmHg), some deterioration in the systolic time intervals occurs with time, but a stimulation persists at the time of death compared to the prehypoxic values.