Relationship between systolic time intervals and arterial blood pressure

It has been suggested that systolic time intervals (STI) can be used to monitor the cardiac effects of antihypertensive treatments and also to evaluate hypertensive patients. STI changes observed in hypertensives have been ascribed to myocardial disease, although they could be due to the existence of a relationship between STI and blood pressure. A group of 37 subjects (18 normotensives and 19 hypertensives) with no signs of heart failure and left ventricular dysfunction were studied to examine the relationship of STI to blood pressure. Pacing with an external battery pulse generator was performed at the rate of 95 beats/min in order to eliminate differences in heart rate. STI were measured from good quality high speed (100 mm/s) recordings and the average value of 10 consecutive cardiac cycles was used for statistical analysis. Normal subjects showed significantly lower values of pre-ejection period (PEP), electromechanical systole (QS2), and pre-ejection period/left ventricular ejection time ratio (PEP/LVET). Moreover, a significant inverse relationship between diastolic pressure and LVET and significant direct relationships between diastolic pressure and PEP, systolic pressure and PEP, diastolic pressure and PEP/LVET, and between systolic pressure and PEP/LVET were demonstrated. We suggest to consider the relation of STI to blood pressure to provide regression equations to best appreciate and use STI.     

Systolic time intervals in Duchenne muscular dystrophy: evaluation of left ventricular performance

The purpose of this study was to evaluate the prevalence of latent cardiac heart failure in Duchenne's muscular dystrophy (DMD). Systolic time intervals (STI) were measured in a cross-sectional study of a group of 177 patients 6-21 years old. Total electromechanical systole (QS2), left ventricular ejection time (LVET), and pre-ejection period (PEP), were corrected for heart rate by means of regression equations obtained from 33 normal subjects (QA2 I, LVET I, PEP I). Mean STI values were significantly different from those observed in an age-matched control group. PEP I was prolonged, LVET I was abbreviated, while QS2 I remained unaltered. STI varied significantly with age. Abnormal values were uncommon before age 10 years. The most critical period was 14-16 years, with an abrupt increase in prevalence from 35 to 72%. Such changes point to the practical use of the STI for clinical decision making especially for surgery.     

Abnormal systolic time intervals in obesity and their relationship with the amount of overweight

We studied 17 severely obese subjects (age range 26 to 42 years), without hypertension, diabetes mellitus, angina, or clinical signs of heart failure or respiratory disease, and 16 age-matched control subjects. X-teleroentgenographic findings (transverse cardiac diameter and cardiothoracic ratio), blood pressure, and mechanocardiographic parameters were analyzed in both groups. By means of conventional simultaneous recordings of ECG, phonocardiogram, and carotid pulse (100 mm/sec), systolic time intervals were calculated as mean values from 10 beats in the morning. The following comparisons were made by means of analysis of variance: heart rate, preejection period (PEP), rate-corrected PEPI (PEPI), left ventricular ejection time (LVET), and QS2 interval (QS2); the latter two were both corrected for heart rate, respectively, as LVETI and QS2I and the PEP/LVET ratio. Abnormal x-ray data were shown in the obese group along with higher values for heart rate, PEP, PEPI, and PEP/LVET and a shorter LVETI; there were no differences in QS2I or blood pressure. There was a correlation between the amount of overweight and, respectively, transverse cardiac diameter (r = 0.84), heart rate (r = 0.69), PEP (r = 0.49), PEPI (r = 0.59), LVETI (r = -0.61), and PEP/LVET ratio (r = 0.72). A correlation was also found between transverse cardiac diameter and PEP/LVET (r = 0.67). We conclude, therefore, that abnormalities in the mechanocardiographic parameters are related to cardiac enlargement, suggesting a preclinical cardiac dysfunction secondary to chronic cardiocirculatory overload in severe obesity. Thus systolic time intervals appear to be affected by preclinical abnormalities of cardiac performance in these subjects.     

Non-invasive evaluation of left ventricular function (systolic time interval) in patients using double-chamber pacemakers programmed on DDD and VVI

OBJECTIVE: To evaluate changes on left ventricular function as assessed by systolic time intervals (STI), by programming "physiological" pacemakers either on VVI or DDD mode. STUDY DESIGN: Comparison of STI values--electromechanical systole (QS2); left ventricular ejection time (LVET); pre-ejection period (PEP); PEP/LVET--in patients submitted to double chamber pacing programmed in DDD or VVI mode. SETTING: Cardiac Pacing Center in a Department of Cardiology at a University Hospital. PATIENTS: We have studied 12 patients (3 men, 9 women), mean age 56.16 years (range 25-76 years) treated with double chamber pacing. INTERVENTIONS: Initial measurements of STI in DDD or one week in VVI mode, and again after one week in DDD mode. RESULTS: Significant changes were found after the first week in VVI pacing, versus baseline determination in DDD pacing, for LVET, PEP, and PEP/LVET (p less than 0.05). At the end of the second week (DDD pacing), there were also statistically significant differences for QS2 (P less than 0.05), LVET (P less than 0.01) and PEP/LVET (P less than 0.05) values when compared with the ones obtained in VVI pacing, at the end of the preceding week. No significant changes were found between the initial and the final STI determinations (both in DDD pacing). CONCLUSION: We concluded for a better performance of the left ventricle at rest when "physiological" pacing is compared with VVI pacing.     

Systolic time intervals in chronic severe anaemia and effect of diuretic and digitalis.

Systolic time intervals were measured from simultaneous high speed recordings of the electrocardiogram, phonocardiogram, and carotid artery pulse in 15 men with chronic severe anaemia not in heart failure and with a normal heart size, and in 15 normal men. Heart rates, electromechanical systole (QS2), pre-ejection period index (PEPI), left ventricular ejection time index (LVETI), and the ratio of pre-ejection period to left ventricular ejection time (PEP/LVET) did not differ significantly in the two groups. After the intravenous administration of frusemide in 10 of the anaemic patients, the pre-ejection period index was prolonged, the PEP/LVET ratio increased, heart rate increased, and the left ventricular ejection time index shortened. Intravenous digoxin did not alter the QS2 interval and heart rate significantly in the anaemic subjects. Left ventricular function in chronic severe anaemia as measured by systolic time intervals does not differ from that of normal controls. The effect of frusemide on the systolic time intervals is explained as an effect of the fall in preload, bringing cardiac function further down on the ascending limb of the Frank-Starling curve. Other related studies are discussed.     

New criteria to increase the reliability of systolic time intervals in left bundle branch block and right ventricular pacing

We measured the systolic time intervals (STI) in 14 patients (pts) with intermittent left bundle branch block (LBBB) in order to find correlations and comparisons in their values which might pertain to the individual patients, with (b) and without (a) LBBB. QS2I, PEP and the PEP/LVET ratio increased significantly (b) while the LVET I did not change. STI correlation was significant and improved further when the QS2 (b) was corrected by subtracting from it the QRS prolongation (b) in msec. All 7 pts with a PEP/LVET ratio (b) greater than 0.65 had an (a) ratio greater than 0.42 (normal limits for our laboratory), sensitivity 100%. Six of 7 patients with a PEP/LVET (b) less than 0.65 had an (a) ratio less than 0.42 (specificity 87.5%). For the individual patient with LBBB his STI can be quite accurately assessed by subtracting from his QS2 (b) the prolongation of the QRS (b) greater than 80 msec the length of the normal QRS duration. The above data were prospectively evaluated in 10 pts to whom intermittent right ventricular pacing was applied. We found that the correction of the QS2 interval for QRS prolongation permitted a very reliable calculation of the STI.     

Effects of propranolol and atenolol on plasma renin activity and systolic time intervals in borderline hypertension

Plasma renin activity (PRA) and systolic time intervals (STI), including total electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP) and isovolumetric contraction time (ICT), were measured in patients atenolol and propranolol. Both beta blockers caused a similar fall in blood pressure and heart rate (P less than 0.001). QS2, PEPc and PEP/LVET values did not change after treatment. Propranolol prolonged ICT (p less than 0.001) and reduced LVET (p less than 0.001). No significant changes were detected in PRA after atenolol while a reduction was found after treatment with propranolol (p less than 0.001). No relationship was found between PRA and STI, however a linear correlation was recorded between systolic pressure and PRA (r = 0,91; p less than 0.01) before beta-blockade. These results suggest that: a) only beta-adrenoceptors are involved in the release of renin; and b) the effect of beta-blockers on STI follows a reduction of blood pressure and heart rate which in turn affect afterload.     

Modification of blood pressure and systolic time intervals by diuretics and beta-blockers in essential hypertension

Heart rate (HR), blood pressure and systolic time intervals (STI), including total electromechanical systole (QS2), left ventricular ejection time (LVETc), pre-ejection period (PEPc), the PEP/LVET index and the time to the peak of carotid upstroke (Ut), were measured in 24 patients with moderate essential hypertension after 15 days of treatment with oral furosemide (F), hydrochlorothiazide (H), propranolol (P), atenolol (A), furosemide + propranolol (F + P) and hydrochlorothiazide + propranolol (H + P). Except F, all treatments significantly reduced blood pressure; maximal reductions were brought about by A and H + P. The heart rate was most reduced by A. THe QS2c interval was reduced only after F and H, LVETc was significantly reduced by H, A and H + P. Drug combinations prolonged PEPc, while the PEP/LVET index was increased only by H + P. Beta-blockers significantly prolonged the Ut. It is concluded that diuretics shorten QS2c mainly through reduction in blood volume. The H + P combination diminishes contractility and cardiac output and should not be employed in heart failure.     

Influence of heart rate on systolic time intervals: Effects of atrial pacing versus dynamic exercise

The effects of atrial pacing and dynamic exercise in the supine position on systolic time intervals (STI) were compared in 10 normals. In another group of 13 normals, the effect of exercise alone on STI was tested. A linear shortening of electromechanical systole (QS₂) and left ventricular ejection time (LVET) with increasing heart rate was demonstrated with right atrial pacing and dynamic exercise in the frequency range between 60 and 140 beats/min. However, the shortening of LVET was significantly less (p<0.01) with exercise compared to pacing. This is explained by an increase in left ventricular stroke volume with exercise. The pre-ejection period (PEP) was significantly (p<0.001) shortened with exercise, but there was no change with atrial pacing. Thus, changes in heart rate (HR) alone, without changes in the dynamic state of the heart, did not influence PEP. It is suggested that PEP at rest should not be corrected for heart rate. The supine exercise regression equations for correction of heart rate for LVET and PEP differ from both the resting and the upright exercise regression equations. With exercise a frequency correction of STI using regression equations should be abandoned. Instead, uncorrected STI at standard heart rates (e.g., 100, 110, and 130 beats/min) should be taken for comparison. Heart rate standardization should be employed using the formula     

Changes in systolic time intervals during physical training in patients with ischemic heart disease. Effect of beta-blockade

Systolic time intervals (STI) were measured at rest before and after an exercise training programme in 37 patients with ischemic heart disease; 17 patients were treated with a beta-blocking drug (BB-group) and 20 were not (nBB-group). After the training period peak oxygen uptake had increased by 37% in the BB-patients and by 41% in the nBB-group. During the training period electromechanical systole (QS2) and pre-ejection period (PEP), when corrected for heart rate, shortened significantly in all 37 patients. Left ventricular ejection time (LVET) increased but when corrected for heart rate no significant changes occurred. The ratio of PEP/LVET decreased significantly. The changes in STI were similar in the patients treated with beta-blocking drugs than in those without such treatment. The changes in STI in both groups suggest that left ventricular function improves during the training period and that beta-adrenergic blockade does not alter this outcome.     

Systolic time intervals in adolescents with insulin-dependent diabetes mellitus

Systolic time intervals were used to evaluate left ventricular performance in 20 diabetic adolescents with a mean age of 15.2 +/- 2.2 years (range 9-17 years) and were compared with an age- and sex-matched control group. Pre-ejection period index (PEPI), left ventricular ejection time index (LVETI), total electromechanical systole index (QS2I) and the PEP to LVET ratio were calculated at rest and following sustained isometric handgrip (SIHG). None of the diabetics had demonstrable microangiopathy or autonomic neuropathy. There was no significant difference in resting or post-exercise heart rate, PEPI, LVETI or PEP/LVET ratio between the two groups. QS2I was significantly prolonged (p less than 0.05) at rest in the diabetics, but was not significantly different following SIHG. These results indicate that cardiac contractility is not detectably abnormal in young diabetics, compared to their adult counterparts who may develop impaired myocardial performance.     

Effect of exercise on left ventricular ejection time in patients with prolapsing mitral leaflet syndrome.

The effect of exercise on left ventricular ejection time was determined in 12 subjects with prolapsing mitral valve leaflet syndrome (PML). A single lead ECG (CM5), phonocardiogram and carotid pulse contour were recorded simultaneously with the subjects at supine rest before and immediately after multistage treadmill exercise. Systolic time intervals were measured from five consecutive complexes to determine the pre-ejection period (PEP), left ventricular ejection time (LVET) and total electromechanical systole (QS2). LVET was corrected for heart rate and defines as LVETc. In nine subjects, an increase of 1 to 49 msec was observed in the LVETc following exercise. A shorter resting LVETc and greater afterload at peak exercise was related to an increase in LVETc of 10 msec or more. Exercise elicited or evoked evidence of left ventricular dysfunction. The results support the concept that impaired left ventricular performance is a concomitant of this syndrome.     

SYSTOLIC TIME INTERVALS IN THYROID DISEASE

The systolic time intervals; total electro-mechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP), and ratio of PEP/LVET were measured from external readings in twenty hyperthyroid and fifteen hypothyroid patients. The hyperthyroid subjects showed shortening of the PEP and reduction in the PEP/LVET. The hypothyroid group showed lengthening of the PEP, shortening of the LVET and increased PEP/LVET. These changes returned towards normal in ten patients rendered euthyroid with appropriate therapy. The value of these measurements to predict the thyroid status was examined in a mixed group of seventy-four patients. There was close agreement between diagnosis predicted from systolic time intervals and that made independently from clinical and biochemical assessment, suggesting that the systolic time intervals may have been a useful place in the clinical assessment of thyroid patients.     

Noninvasive evaluation of left ventricular function in chronic severe anemia

Left ventricular function was evaluated noninvasively in cases of chronic severe anemia (CSA) by recording systolic and diastolic time intervals (STI and DTI). These time intervals were recorded in 38 patients with CSA (hemoglobin below 7 g%), without cardiac decompensation, and in 30 control subjects. STI and DTI were measured from the simultaneous recordings of the apexcardiogram, carotid arterial pulse, electrocardiogram and phonocardiogram. The left ventricular ejection time was significantly prolonged (p less than 0.02), and associated with marked shortening of the PEP and reduction of the PEP/LVET ratio (p less than 0.001 in each case) in cases of CSA as compared to controls. Regarding the DTI, there was significant shortening of total filling time, slow filling time (p less than 0.001 in each case) and atrial systole (p less than 0.01) with no appreciable change in rapid filling time and isovolumic relaxation time. The SFT/RFT ratio and a/H ratio (the amplitude of the a-wave relative to the total height of the apexcardiogram) showed significant reductions (p less than 0.001 in each case). These changes in STI and DTI indicate enhanced left ventricular performance during diastole followed by faster and more complete relaxation during diastole in CSA.     

Systolic time intervals in essential hypertension. I. Study of untreated patients]

15 patients with Stage II (VHO Classification) hypertension were studied before treatment. The following systolic time intervals were measured: 1) total electromechanical systolic period (QS2); 2) left ventricular ejection time (LVET); 3) interval between the first and second sounds (S1 S2); 4) pre-ejection period (PEP); 5) interval between the start of QRS and the first sound (QS1); 6) isovolumetric contraction time (ICT); 7) PEP/LVET ratio. The values measured were compared to the theoretical values obtained by the Weissler regression methods, taking into consideration the sex of the patient and the heart rate. QS1 and the ICT were both a slightly longer than normal; the PEP was increased by 25.6% (26.8 ms), whilst the LVET was decreased by 7.9% (24.0 ms), both differences being significant; QS2 increased by 1.1% (to 4.9 ms) but this was not significant; the PEP/LVET ratio was 0.479 +/- 0.12. These results seem to characterise moderate systemic hypertension with a significant relation between the variations of PEP, LVET and PEP/LVET with the diastolic blood pressure; although they have no absolute value, these results may be used in a longitudinal study to follow the course of hypertension and to study the effects of treatment.     

Left ventricular function and adrenergic hyperactivity before and after saphenous vein bypass.

Forty patients with severe angina pectoris were studied before and two weeks after saphenous vein bypass surgery (SVG) in order to assess the effect of this operation on left ventricular performance as judged by systolic time intervals (STI). The patients were divided into two groups: group I included 29 patients in whom no postoperative infarction occurred and group II was composed of 11 patients with postoperative infarction. For group I the PEP/LVET was 0.39 +/- 0.01 preop and slightly but significantly increased at 0.42 +/- 0.004 (P less than 0.025) two weeks postop. The mean preop PEP/LVET was 0.33 +/- 0.01 for group II and dramatically increased to 0.54 +/- 0.02 (P less than 0.001) after surgery. Another striking abnormally was a marked shortening of electromechanical systole (QS2I), which was uniformly present in the postoperative studies. Follow-up studies in 16 patients and urinary catecholamine determination in five patients suggested excessive adrenergic activity was responsible for the abbreviated QS2I. This phenomenon must be considered when interpreting the results of SVG on left ventricular function.     

Left Ventricular Function in Newly Diagnosed Non-insulin-dependent (Type 2) Diabetics Evaluated by Systolic Time Intervals and Echocardiography

ABSTRACT Systolic time intervals (STI) and echocardiography were recorded in 133 (70 men, 63 women) newly diagnosed non-insulin-dependent diabetics aged 45–64 years and in 144 (62 men, 82 women) non-diabetic control subjects of the same age. Both male and female diabetics had significantly increased pre-ejection period/left ventricular ejection time ratio (PEP/LVET) in STI as compared with the respective non-diabetic control subjects. Male diabetics showed a reduced ejection fraction (EF) in echocardiography, but no significant difference was found in this respect between female diabetics and controls. A significant negative correlation was found between 2-hour postglucose serum insulin level and EF in male and female diabetics. After adjusting for the effect of age, coronary heart disease, hypertension, obesity and haemoglobin concentration, male diabetics still had a higher PEP/LVET ratio and a lower EF than male controls. In women, no significant differences were found between diabetics and controls in the PEP/LVET ratio or EF adjusted for the above factors. The results of this study are compatible with the view that impaired left ventricular function may be an early phenomenon in the clinical course of non-insulin-dependent diabetes.     

Echocardiographic estimation of pulmonary artery pressure in transposition of the great arteries

To determine their usefulness in estimating pulmonary artery pressure, left ventricular systolic time intervals (STI) were determined by echocardiography in 65 patients with dextro-transposition of the great arteries (TGA). The STI were measured from recordings of pulmonary valve motion at 100 mm/sec paper speed. The pre-ejection period (PEP) and the ratio of PEP to left ventricular ejection time (PEP/LVET) were directly related to pulmonary artery pressure. The strongest correlations were that between PEP/LVET and pulmonary artery diastolic pressure (r = 0.70) and that between PEP/LVET and the ratio of mean pulmonary pressure to mean systemic pressure (r = 0.71). A value of PEP/LVET of less than 0.26 was consistently associated with pulmonary artery diastolic pressures of less than 20 mm Hg and, in 28 of 31 patients, pulmonary artery pressure less than one-third of mean systemic arterial pressure. Pulmonary hypertension was present in 18 of 22 patients with PEP/LVET of 0.30 or greater; elevated PEP/LVET was also present in four patients with abnormalities of cardiac rhythm or conduction, two of whom also had angiographic evidence of myocardial dysfunction.     

Left ventricular performance in cases with chronic renal failure. A study of systolic time intervals

Left ventricular (LV) functions as reflected in systolic time intervals (STIs) were studied in 28 patients with chronic renal failure (CRF) and in an equal number of age and sex matched normal controls. Measurement of STIs revealed that mean total electromechanical systole (QS2) and left ventricular ejection time (LVET) were significantly decreased, whereas isovolumic contraction time (IVCT) was significantly increased in patients with CRF as compared to controls. Mean PEP/LVET ratio did not show any significant change. Eleven cases of CRF had congestive heart failure, and in 9 of them the PEP/LVET ratio was normal. Seven cases of CRF had evidence of left ventricular dysfunction (PEP/LVET greater than 0.4). In 6 cases, STIs were also recorded following dialysis, and revealed an increase in PEP, IVCT and PEP/LVET and a decrease in QS2 and LVET, but none of these changes were statistically significant. It is concluded that only a small percentage of cases of renal failure show LV dysfunction. However, signs of congestion are seen in a greater number of cases. These are not necessarily indicative of LV dysfunction but may be due to fluid and electrolyte overloading.     

运动负荷对左室收缩时间间期的影响

用多道生理记录仪对６７例被检者（其中正常人３７例，高血压病人３０例）分别测定双倍二级梯运动前、运动后１、３、５、７ｍｉｎ的收缩时间同期（ＳＴＩ）。结果显示，运动后１ｍｉｎ和运动前相比，表现为ＥＭＴＬＶＥＴ、ＰＥＰ、ＥＭＬ、ＩＣＴ、ＨＷＴ缩短，ＰＥＰ／ＬＶＥＴ、ＩＣＴ／ＬＶＥＴ、ＴＨ／ＴＨ比值减小。运动停止后，以上各指标逐渐恢复，但正常人组的恢复过度较高血压病组快，提示高血压病人尽管安静休息时ＳＴＩ正常，但心功能代偿能力和调节能力已有所下降。本文分析了运动负荷对ＳＴＩ影响的可能机理，并认为，测定动态下的ＳＴＩ能更好地显示心脏的储备和调节能力。