Shortening of electromechanical systole as a manifestation of excessive adrenergic stimulation in acute myocardial infarction

Using cardiac phase to order reconstruction (CAPTOR): a method to improve diastolic images

A method is proposed to reconstruct multiphase images that accurately depicts the entire cardiac cycle. A segmented, gradient-recalled-echo sequence (FASTCARD) was modified to acquire data continuously. Images were reconstructed retrospectively by selecting views from each heartbeat based on cardiac phase rather than the time elapsed from the QRS complex. Cardiac phase was calculated using a model that compensates for beat-to-beat heart rate changes. Images collected using cardiac phase to order reconstruction (CAPTOR) depict the entire cardiac cycle and lack the temporal gap that is characteristic of prospectively reconstructed sequences. Time-volume curves of the left ventricle capture the contribution of atrial contraction to end-diastolic volume (EDV). Transmitral phase-contrast flow measurements show a second peak inflow (alpha wave) that is absent in the standard sequence. Because atrial contraction contributes to ventricular EDV, images using CAPTOR potentially may provide a more reliable measure of EDV, stroke volume, and ejection fraction than standard techniques.

Relation between diastolic perfusion time and coronary artery stenosis during stress-induced myocardial ischemia

BACKGROUND

Experimental studies have demonstrated that during stress-induced myocardial ischemia, coronary obstruction and diastolic perfusion time are factors that limit subendocardial perfusion and correlate to degree of myocardial dysfunction. The relation between these two factors has not yet been investigated in humans. The aim of the present study was to assess the relation between diastolic perfusion time and degree of coronary stenosis during different types of stress tests.

METHODS AND RESULTS

Nine patients with isolated and proximal stenosis of the left anterior descending coronary artery were selected. Patients underwent three different randomized stress tests (upright, supine bicycle stress test, and transesophageal atrial pacing). Diastolic perfusion time, heart rate (RR interval), and systolic and diastolic pressures were measured during the test and at the ischemic threshold (0.1-mV ST-segment depression). Angiographic measurements of coronary stenosis were evaluated by quantitative coronary angiography. At the ischemic threshold, significant differences among tests were found in heart rate (P < .05), systolic pressure (P < .001), and diastolic pressure (P < .05). In each stress test, diastolic perfusion time at the ischemic threshold was closely correlated with minimal stenosis diameter (r = .97; P < .001) and percent diameter stenosis (r = .92; P < .001) with no difference among the tests. In contrast, heart rate, rate-pressure product, and time to ischemic threshold were not significantly correlated with percent diameter stenosis and minimal stenosis diameter. No significant correlation was observed at the ischemic threshold between diastolic perfusion time and corresponding values of heart rate, despite the close correlation at rest (r = .95; P < .001).

CONCLUSIONS

Despite differences in associated hemodynamic responses to various stress tests, a close relation exists between stenosis severity and diastolic perfusion time at the onset of stress-induced myocardial ischemia. Therefore, diastolic perfusion time at the ischemic threshold may be an indirect estimate of the hemodynamic significance of coronary stenosis.

Weight carrying effects on treadmill exercise response in persons without heart disease

To evaluate the effect of weight carrying on dynamic exercise response, 12 normal subjects were studied during treadmill exercise using ear densitography in two ways: (1) no weight, (2) 10 kg weight in one hand. Although there were no significant differences in diastolic time (DT), tension-time index [TTI: systolic blood pressure x heart rate (HR) x left ventricular ejection time (LVET)] was significantly higher throughout the weight carrying exercise compared to dynamic exercise. The amount of change (delta) in TTI was significantly larger in the initial stage (control to 1 min) of weight carrying exercise compared to dynamic exercise, but there were no significant differences in the later stages (1-3 min and 3-6 min). A prolongation in LVET was observed despite increasing HR during the first minute of exercise in both type of exercise, but LVET was longer at any given HR in weight carrying compared to dynamic exercise. Thus, despite higher TTI throughout the weight carrying exercise, delta TTI was larger only in the initial stage which was caused by prolongation of LVET resulting from disproportionate increase in venous return of early exercise.

Cardiovascular responses to autonomic stimuli in workers with vibration-induced white finger

Cardiovascular responses to autonomic stimulation were assessed in 11 grinding operators affected with vibration-induced white finger (VWF) and in 11 comparable healthy controls by measuring blood pressures, heart rate and systolic time intervals (STI) during a hand-grip test, an arithmetic test and an orthostatic test. Digital circulatory function was also investigated by measurement of finger systolic pressure (FSP) during local cooling with water at 30 degrees C, 15 degrees C and 10 degrees C. The increase in diastolic blood pressure and heart rate during the stress tests was greater in the VWF workers than in the controls. The STI values such as total electromechanical systole and left ventricular ejection time, were found to be shorter in the VWF subjects than in the controls at rest and during both the circulatory stress tests and the recovery periods (0.001 less than p less than 0.05). Multiple regression analysis showed that vibration exposure was the major predictor of STI during the stress tests, while age, smoking and drinking habits did not contribute substantially to the explained variation in STI. The reduction in FSP by local cooling from 30 degrees C to 15 degrees C and 10 degrees C was greater in VWF operators than in controls (p less than 0.001), and total closure of the digital arteries at 10 degrees C was observed in 8 VWF workers (72.7%). In all subjects significant relationships were found between the reduction in FSP at 10 degrees C and the decrease in STI during circulatory stress activities (p less than 0.001). The findings in this study suggest an association between vibration exposure, digital vasospasm and increased cardiac sympathetic tone, the latter being demonstrated by the shortening of STI during the stress tests. It is suggested that excessive sympathetic reflex activity plays the dominant role in the pathogenesis of VWF.

The QT and QS2 intervals in patients with mitral leaflet prolapse

The QT interval was plotted against the R-R interval in 92 patients with mitral prolapse and 92 age- and sex-matched control subjects. Ten patients (11%) lay above the upper 95% confidence limit for the control group, and analysis of variance confirmed a small group effect (p less than 0.05). Despite this, the mean QT intervals in the two groups differed by only 7 msec and a t test showed no significant difference between the groups. The prevalence of QT prolongation was exaggerated by Bazett's rate correction formula (62%) or historical control groups published by Simonson (58%) or Ashman (70%). Simultaneous QT and QS2 intervals were measured in 67 patients with mitral prolapse. Inversion of the normal QT:QS2 relationship occurred in nine patients (13%) and was more common in the presence of severe mitral regurgitation. It was not associated with an increased prevalence of absolute QT prolongation and was therefore thought to be caused by relative shortening of the QS2 interval. In conclusion, the prevalence of QT prolongation in mitral prolapse is low (11%). The QT:QS2 ratio is unlikely to be a reliable indicator of QT prolongation in these patients.

Effect of exercise on ventricular diastolic time in coronary artery disease

To evaluate diastolic time during uninterrupted upright exercise, 28 normal volunteers (group 1) and 12 men with coronary artery disease (group 2) were studied by ear densitography. Electromechanical systole-heart rate and diastolic time-heart rate regression equations during upright exercise were obtained from group 1. Electromechanical systole-heart rate had an inverse linear relation (electromechanical systole = 480 - 1.4 heart rate) and diastolic time-heart rate had an inverse nonlinear relation (diastolic time = 1206e-0.02 heart rate). Although there were no significant differences in electromechanical systole and diastolic time at 1 minute of exercise between patients with and without CAD, at peak exercise prolongation of electromechanical systole and consequent shortening of diastolic time in patients with CAD were observed. This disproportionate shortening of diastole with lengthening of systole at peak exercise tends to decrease myocardial perfusion and, hence, oxygen supply, while increasing myocardial oxygen demand, contributing to aggravation of ischemia in patients with CAD.

Noninvasive evaluation of the effect of timolol on left ventricular performance after myocardial infarction and the consequence for prognosis

Left ventricular performance was evaluated noninvasively in 111 patients participating at one study center in the Norwegian Multicenter Study on Timolol After Myocardial Infarction. Systolic time intervals were measured in 55 patients treated with timolol and in 56 patients receiving placebo. Measurements were made before randomization, and after 1, 3 and 12 months of treatment. During the treatment period, the pre-ejection period/left ventricular ejection time ratio was significantly lower in the timolol-treated group, indicating better left ventricular function than in the placebo-treated patients. In the 27 patients who died during the follow-up period of 50 to 72 months, there was a significant increase in the pre-ejection period/left ventricular ejection time ratio from baseline to the last performed recording, indicating a deterioration in left ventricular performance in these patients. No such change occurred in the group that survived the entire follow-up period. Deterioration of left ventricular function is related to a high long-term mortality rate after myocardial infarction, and left ventricular function is better preserved in patients treated with timolol than in patients receiving placebo.

Non-invasive evaluation of autonomic tone changes during isometric exercise in normal subjects and in patients with coronary artery disease

In order to evaluate the clinical implications of QT/QS2 ratio during manoeuvres of sympathetic stimulation we studied the effects of handgrip (75% of maximal voluntary contraction) in 18 middle-aged normal subjects and in 16 patients with previous myocardial infarction. We also evaluated the effects of propranolol (0.1 mg/kg i.v.) in all normal subjects and in 10 of the 16 patients with coronary artery disease. At rest the two groups had similar heart rate, blood pressure, QT, QS2 and QT/QS2 ratio values. A significant increase in heart rate and systolic blood pressure was recorded during handgrip both in normal subjects and in patients with coronary artery disease; QT/QS2 significantly increased in normal subjects but did not show significant variations in patients with coronary artery disease, with significant differences between the two groups at peak exercise. Handgrip-induced QT/QS2 changes showed a marked variability both in normal and diseased subjects. After propranolol, QT/QS2 showed no significant difference at peak exercise in the two groups. The variability of ratio changes was nullified by the administration of the drug. These findings suggest that handgrip-induced QT/QS2 changes might be an expression of beta-adrenergic discharge. The clinical value of handgrip-induced QT/QS2 changes in detecting patients with coronary artery disease is limited by the variability of the response of the ratio observed in the two groups.

Some pathophysiological aspects of vibration-induced white finger

The level of sympathetic nervous activity was assessed by evaluating cardiovascular responses to a cold test in 63 vibration-exposed workers (50 subjects without vibration white finger (VWF) and 13 subjects at stages 1 and 2 of VWF) and in 41 controls. Blood pressure, heart rate, systolic time intervals and the skin temperature of the third finger of the right hand were monitored throughout the cold test period. Basal urinary excretion of free catecholamines and platelet aggregation indices both in vitro and in vivo were also determined in all subjects. Systolic time intervals such as electromechanical systole index (QS2I) and left ventricular ejection time index (LVETI) were found to be shorter in the vibration-exposed workers with and without VWF than in the controls, both at rest and during cold exposure and recovery (p less than 0.001). A significant inverse relationship between urinary free catecholamines and the duration of LVETI was observed under resting conditions (p less than 0.03). The recovery rate of the basal finger skin temperature after local cooling was slower in vibration workers with VWF than in those without VWF (p less than 0.05) and in the controls (p less than 0.001). Platelet aggregation indices were similar in all groups studied. The results suggest that the level of sympathetic nervous activity is higher in vibration-exposed workers than in controls. In subjects with VWF, sympathetic hyperactivity in combination with local factors such as vibration-induced hyperresponsiveness to cold of the digital vessels may be responsible for finger blanching attacks.(ABSTRACT TRUNCATED AT 250 WORDS)

Therapeutic effect of taurine in congestive heart failure: a double-blind crossover trial

In a double-blind, randomized, crossover, placebo-controlled study, we investigated the effects of adding taurine to the conventional treatment in 14 patients with congestive heart failure for a 4-week period. Compared with placebo, taurine significantly improved the New York Heart Association functional class (p less than 0.02), pulmonary crackles (p less than 0.02), and chest film abnormalities (p less than 0.01). A benefit of taurine over placebo was demonstrated when an overall treatment response for each patient was evaluated on the basis of clinical examination (p less than 0.05). No patient worsened during taurine administration, but four patients did during placebo. Pre-ejection period (corrected for heart rate) decreased from 148 +/- 14 ms before taurine treatment to 137 +/- 12 ms after taurine (p less than 0.001), and the quotient pre-ejection period/left ventricular ejection time decreased from 47 +/- 9 to 42 +/- 8% (p less than 0.001). Side effects did not occur in the patients during taurine. The results indicate that addition of taurine to conventional therapy is safe and effective for the treatment of patients with congestive heart failure.

Diastolic time during recovery from upright exercise in persons without heart disease

To assess the relation between heart rate and diastolic time (cardiac cycle minus electromechanical systole) during the recovery period from upright exercise, 12 normal volunteers were studied immediately after and 2 and 5 minutes after exercise in the upright position. Although heart rate was significantly lower at 5 minutes compared with 2 minutes after exercise (106 vs 116 beats/min), there was significant shortening of diastolic time (from 251 to 230 ms) and total diastole per minute (from 28,634 to 24,220 ms/min). The explanation of this phenomenon appears to be disproportionate lengthening of diastolic time at 2 minutes after exercise, which must represent physiologic response due to increased left ventricular filling as well as continuing adrenergic effects, which would be diminished at 5 minutes. This lengthening of diastolic time also would maintain decreased subendocardial blood flow caused by increased end-diastolic volume.

QT/QS2 ratio as an index of autonomic tone changes

The effects of changes in sympathetic tone on QT/QS2 ratio were studied in 10 healthy subjects aged 21 to 24 years. The subjects underwent a bicycle ergometer exercise, a tilt test, a decrease in carotid transmural pressure induced by means of pneumatic neck chamber, an i.v. injection of phenylephrine. A phonocardiogram and ECG were simultaneously recorded at a paper speed of 100 mm/s to evaluate QT and QS2 intervals in each test. In basal conditions, the QT/QS2 ratio was less than 1, whereas it increased progressively during the physical exercise and became greater than 1 at peak exercise. Both the upright position and the increase in neck-tissue pressure induced a significant increase in the QT/QS2 ratio as compared with the basal values, whereas i.v. administration of phenylephrine reduced significantly the QT/QS2 ratio. These results demonstrate that those stimuli which induce a rise in adrenergic activity may increase the QT/QS2 ratio. In contrast, the reflex inhibition of the adrenergic activity induced by phenylephrine is accompanied by a reduction in QT/QS2 ratio. Therefore, the QT/QS2 ratio might represent a reliable index of sympathetic cardiac tone.

Systolic time intervals: a review of the method in the non-invasive investigation of cardiac function in health, disease and clinical pharmacology

Measurement of systolic time intervals is a valuable, non-invasive procedure to assess left ventricular performance, particularly when influenced by drugs. In this review, we discuss various factors affecting systolic time intervals, the therapeutic implications of the technique and its place among other non-invasive tests of cardiac function.

Haemodynamic effects of BM 10.188, a new orally active inotropic agent, in healthy volunteers

1 BM 10.188 (Doxaminol, Boehringer Mannheim, GmbH) is a recently developed beta-sympathomimetic agent which has shown promising positive inotropic activity in experimental animal models. It is a dibenzoxepine derivative. 2 The effects of 20 mg oral BM 10.188 on systolic time intervals and standard echocardiographic parameters have been studied in six normal healthy male volunteers. 3 When assessed by repeated measured analysis of variance, QS2 and LVET shortened significantly (P less than 0.005) in the 8 h period following BM 10.188. Mean maximum shortening values were: QS2, 25.7 +/- 25.6 (s.d.) ms at 155 min and LVET, 10.7 +/- 9.5 (s.d.) ms at 155 min. There was a corresponding small but significant increase of 4.2 +/- 3.9 (s.d.) ml in stroke volume at 6 h (P less than 0.025). 4 These results indicate that in normal volunteers, BM 10.188 exhibits effects on noninvasive cardiological indices similar to those observed after cardiac glycosides.

Comparison of the inotropic and chronotropic effects of metoprolol and propranolol

The cardiovascular responses to intravenous doses of isoproterenol were measured in eight male volunteers before and during administration of 50 mg metoprolol, orally every 6 hours and 40 mg propranolol, orally every 6 hours for a total of five doses. The dose of isoproterenol required to produce an increase in heart rate of 25 beats/min (the ID25) was 2.0 +/- 1.4 microgram before beta blockade, 6.2 +/- 4.4 microgram during metoprolol, and 44.4 +/- 12.0 microgram during propranolol administration. Similar changes in diastolic blood pressure, QS2I, preejection period, and preejection period/left ventricular ejection time ratio occurred at the ID25 during treatment with both metoprolol and propranolol. In volunteers, propranolol produces a much more intense blockade of the inotropic and chronotropic effects of isoproterenol than does metoprolol.

Cardiovascular effects of theophylline. Partial attenuation by beta-blockade

The effects of theophylline upon cardiovascular function were studied in 8 male subjects, aged 22-33 years, before and during concomitant administration of metoprolol (50 mg every 6 h) and propranolol (40 mg every 6 h). Theophylline, as aminophylline (6.7-7.3 mg/kg) was given over 30 min. The theophylline level five minutes after completion of the aminophylline infusion was 15.9 +/- 1.8 micrograms/ml in the absence of beta blockade, 16.1 +/- 1.7 micrograms/ml during metoprolol, and 15.1 +/- 1.6 micrograms/ml during propranolol. Theophylline produced a 7% increase in mean arterial pressure which was not attenuated by either metoprolol or propranolol. Heart rate was not changed by theophylline. The QS2 Index (QS2I), a sensitive indicator of inotropism, was shortened from 488 +/- 16 to 476 +/- 16 msec (p less than 0.01) by theophylline alone. After administration of metoprolol or propranolol, theophylline produced no shortening of the QS2I. Theophylline has a mild inotropic effect in healthy subjects. This effect is prevented by pretreatment with beta-adrenergic antagonists.

Effect of isocapnic hypoxia on systolic time intervals in conscious man

The effects of progressive isocapnic hypoxia on the systolic time intervals were studied in 10 healthy human subjects. We induced hypoxia by a rebreathing method and monitored the arterial oxygen saturation continuously and non-invasively by means of an ear oximeter. Arterial oxygen saturation (SaO2) was allowed to fall to a level of 75 per cent and was then held constant for five minutes. As SaO2 fell, heart rate increased linearly, with a mean increase of 0.83 beats/min per one per cent fall in SaO2. The pre-ejection phase index decreased from a mean of 127.2 ms at full oxygen saturation to 120.1 ms at steady-state hypoxia levels, while the ratio of the pre-ejection phase to left ventricular ejection time decreased from a mean of 0.330 to 0.301. The left ventricular ejection time index increased from 417.4 ms to 429.3 ms, while no statistically significant difference was found in the length of electromechanical systole.

Beneficial effect of continuation of propranolol through coronary bypass surgery

The safety and beneficial effect of continuation of propranolol (Pr) through coronary bypass surgery (CBS) was studied in two groups of patients. In the control group (50 patients) Pr was discontinued 24 h before CBS without reinstitution afterwards. In the propranolol group the drug was maintained up to 4 to 10 h before surgery and was restarted within 24 h afterwards. The incidence of subendocardial myocardial infarction was significantly lower in the Pr group (1 out of 30 vs 10 out of 50, p less than 0.05) while the incidence of transmural infarction was the same in both groups (3 out of 30, 10%, vs 5 out of 50, 10%). The incidence of supraventricular tachycardias during the first three postoperative days was significantly lower in the propranolol group compared to control (5% vs 30%, p less than 0.01). The 24 h urinary epinephrine and norepinephrine excretion was significantly greater than normal the day before surgery (136 +/- 12 vs 39 +/- 4 micrograms/24 h, p less than 0.01), and was still high two weeks after surgery (115.1 +/- 14 micrograms/24 h). There were no complications related to propranolol. The left ventricular function as measured from the systolic time intervals was the same pre- and postoperatively in both groups. The results of this study show that administration of propranolol up to 4 h before coronary bypass and reinstitution immediately afterwards is safe and beneficial.

Systolic time intervals in atrial fibrillation

Forty patients with atrial fibrillation and 20 patients with congestive heart failure and sinus rhythm were studied. Patients were divided into two groups. Group A consisted of 20 patients with atrial fibrillation in whom systolic time intervals were measured. Twenty to 50 beats were analyzed. Five of the patients had high-fidelity measurements of left ventricular pressure simultaneous with determination of systolic time intervals. Analysis of the systolic time intervals for the entire group showed that the preejection period lengthened at faster heart rates and that the left ventricular ejection time was relatively constant at slower heart rates. This resulted in a progressive increase in the ratio of preejection period over left ventricular ejection time (PEP/LVET) as the heart rate increased. The rate of increase in PEP/LVET was minimal below a heart rate of 75 beats per minute. The increase in preejection period at faster heart rates is due to greater isovolumic developed pressure without a corresponding increase in left ventricular dp/dt. Group B consisted of 40 additional patients (20 with atrial fibrillation and 20 with sinus rhythm). In group B, the total electromechanical systole corrected for heart rate (QS2I) and the levels of digoxin in the blood were compared. The QS2I was significantly shorter in atrial fibrillation (497 +/- 5 msec vs 528 +/- 4 msec; P less than 0.01), while the levels of digoxin in the blood were identical (0.9 +/- 0.1 vs 1.0 +/- 0.1 ng/ml). The results of this study must be considered when systolic time intervals are to be employed in patients with atrial fibrillation.

Safety and rationale for continuation of propranolol therapy during coronary bypass operation

Thirty consecutive patients undergoing coronary bypass were studied. Oral propranolol therapy was maintained up to 4 to 10 hours before operation. Nineteen of the patients had a history of myocardial infarction (MI), 14 had hypoakinetic areas, and 8 had decreased ejection fraction indicating advanced coronary artery disease. Twenty-four-hour urinary epinephrine and norepinephrine obtained the day before operation were markedly increased at 136 +/- 12 microgram per 24 hours (normal, 39 +/- 4 microgram, rho less than 0.01). There were 4 perioperative MIs (13%) and no deaths. Plasma propranolol 1 hour before operation was 43.3 +/- 8 ng per milliliter, indicating good beta blockade. Propranolol was started within 24 hours postoperatively. There were no preoperative, intraoperative, or postoperative complications related to propranolol therapy. We conclude that because of markedly increased adrenergic tone the day before operation and transient hypersensitivity to adrenergic stimulation after withdrawal of propranolol, this agent should be continued through coronary bypass operation.

Use of the systolic time intervals in clinical pharmacology

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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.

The effect of quinidine sulfate on QRS duration and QT and systolic time intervals in man

QRS duration, QT interval, total electromechanical systole (QS(2)), left ventricular ejection time (LVET), and preejection period (PEP) were determined in five male and two female healthy volunteers in a fasting state at hourly intervals for 7 hours during a control period and after administration of 400 mg quinidine sulfate. Changes of QRS duration (delta QRS) and rate-corrected QT interval (delta QTc) were calculated before and after quinidine. Deviations of measured QS(2), LVET, and PEP from the normal were calculated as the differences between the observed interval and those predicted from the normal regression equation. The effect of quinidine on systolic time intervals (delta QS(2), delta LVET, DELTA PEP) were expressed as the differences between the deviations from the normal regression equation during the control period and after the drug administration. After quinidine sulfate delta QRS, delta LVET, delta PEP, and delta PEP, delta LVET were slight and inconsistent. However, delta QTc and delta QS(2) were significant (at P is less than 0.05 or better) from the first hour to the 7th hour and from the 2nd hour to the 5th hour, respectively. The mean maximum delta QTc was 44.8 milliseconds and delta QS(2) was 29.9 milliseconds. The significant changes of QTc and QS(2) seemed to occur at the plasma level range of 0.75-1.9 mug/ml. This study indicates that of the various systolic time interval measurements obtained after quinidine administration, the changes of QT interval and QS(2) are most significant and that these changes seem to occur even at low plasma levels.

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.

Usefulness of systolic time intervals in coronary artery disease

This review summarizes current knowledge concerning the value of systolic time intervals in coronary artery disease. Although the usual pattern of prolongation of the preejection period (PEP) and shortening of the left ventricular ejection time (LVET) characteristic of left ventricular failure is seen in acute myocardial infarction, the systolic time intervals (as well as all other measures) are profoundly influenced by adrenergic hyperactivity characteristics of this disorder. Adrenergic stimulation normally shortens both the PEP and LVET indexes and decreases the PEP/LVET ratio. The degree of shortening of electromechanical systole (QS2) is directed related to the excessive adrenergic tone. Patients with the greatest systolic time interval abnormalities have a poorer prognosis, a greater incidence of congestive heart failure and more abnormalities of directly measured indexes of left ventricular performance. The systolic time intervals are useful for assessing left ventricular performance in chronic coronary artery disease as well. In chronic coronary artery disease the PEP/LVET ratio and angiographically determined left ventricular ejection fraction are closely correlated ( r = -0.76), but the level of this correlation is less than that in other forms of left ventricular disease. The left ventricular ejection time index is prolonged after exercise in patients with angina pectoris when compared with findings in normal subjects. Failure of the ischemic ventricle to respond to adrenergic stimulation is the most likely mechanism. Addition of the postexercise left ventricular ejection time to standard treadmill stress testing identifies a significant number of patients (23 percent) who would have had false negative results by electrocardiographic criteria alone. In addition, this index provides confirmatory evidence in those with apparently positive electrocardiographic test data. The systolic time intervals have been useful in assessing both medical and surgical therapy in coronary artery disease. The test can be performed repeatedly and provides a measure of both left ventricular performance and extent of adrenergic hyperactivity. Thus, evaluation of therapy represents the most useful future application of systolic time intervals.

Usefulness of systolic time intervals in differential diagnosis of constrictive pericarditis and restrictive cardiomyopathy

Systolic time intervals in 15 patients with constrictive pericarditis and seven patients with restrictive cardiomyopathy were compared in order to assess their value in the differential diagnosis of the two disorders. Clinical examination had failed to make the distinction. Right heart catheterization was helpful in diagnosing restriction but failed to differentiate patients with constrictive pericarditis from those with restrictive cardiomyopathy. The systolic time intervals clearly separated the two groups. The PEP/LVET was normal in all patients with constrictive pericarditis (0.34 +/- 0.01) and abnormal in all patients with restrictive cardiomyopathy (0.70 +/- 0.09, P less than 0.001). In 13 patients (five with restrictive cardiomyopathy and eight with constrictive pericarditis) the results of quantitative left ventricular angiocardiography were available. A high correlation (r=-0.90, P less than 0.01) between the PEP/LVET and the ejection fraction confirmed the validity of the PEP/LVET as a measure of left ventricular performance in these patients. Thus the systolic time intervals clearly distinguished between constrictive pericarditis and restrictive cardiomyopathy and are a reliable non-invasive technique for making the difficult differential diagnosis.

Cardiac performance during pregnancy: serial evaluation using external systolic time intervals

Indirect systolic time indices were used to evaluate serial changes in left ventricular function during pregnancy in 13 normal patients and five patients with compensated cardiac conditions. Changes in both groups tended to parallel each other. In both groups, serial LVET index decreased, PEP index increased, and PEP/LVET ratio increased. Q-S2 index decreased in the normal group in midpregnancy and was inconsistent in the cardiac group. In the immediate postpartum period, LVET index returned to baseline values but PEP and PEP/LVET remained increased in both groups. Results of multiple comparison tests demonstrated that the largest (or smallest) value of each systolic time interval during pregnancy was observed in either the periods of the weeks 28 to 34 or 34 to 38. No significant differences were noted in intergroup comparison between the normal and cardiac groups. These data suggest that consistent changes in cardiac function may be determined during pregnancy by the noninvasive technique of indirect systolic time interval evaluation. These changes may reflect a change in left ventricular contractility, preload or afterload. The differences may persist even in the immediate postpartum period when cardiac output and heart rate have decreased to normal, suggesting residual changes in intrinsic left ventricular function. In patients with compensated heart disease, indirect tests of left ventricular function generally reflect the changes in normal pregnant women.

Assessment of left ventricular function following coronary bypass surgery: a non-invasive study

Hardarson, T., Ziady, G. M., and Khattri, H. N. (1974).Thorax, 29, 359-365. Assessment of left ventricular function following coronary bypass surgery: a non-invasive study. In a series of 15 patients with ischaemic heart disease, systolic time intervals (STI) were measured before, and at one week, three months, and six months following coronary vein-graft surgery. Preoperatively, the left ventricular ejection time (LVET) was abnormally short in seven patients, while the pre-ejection period was abnormally long in seven patients, suggesting impaired left ventricular function. At one week after surgery LVET and total electromechanical systole (QA2) were significantly abbreviated. This may be explained by the transient fall in cardiac output or postoperative neurohumoral changes. For the group as a whole, no significant changes were found at three or six months, suggesting that cardiac function was generally preserved rather than improved. However, in individual patients changes in STI correlated with the clinical and angiographic estimate of success of the operative treatment.