Stroke volume and systolic time interval adjustments during bicycle exercise

1979 ◽  
Vol 46 (3) ◽  
pp. 588-592 ◽  
Author(s):  
J. H. Vanfraechem
Keyword(s):  
Stress Response ◽  
Stroke Volume ◽  
Work Load ◽  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Time Interval ◽  
Vo2 Max ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time

By use of the impedance noninvasive method, cardiac output (Q), stroke volume (SV), heart rate (HR), Heather index (HI), and systolic time interval (STI) values were studied in 17 subjects working at 25, 50, and 75% of their maximal oxygen uptake (Vo2 max) on a Monark bicycle. A significant increase in SV at each work load and a concomitant decrease in positive expiratory pressure (PEP), left ventricular ejection time (LVET), and PEP/LVET were observed. The linear regression equation at 75% Vo2 max between LVET and HR and SV confirms the close relationship between these parameters. The significa-t increase of the contractility index (HI) showing the stress response of the myocardium is clearly assessed. At 75% work load, its correlation with SV is low; but the high level of the correlation (r = 0.90) between HI and HR in the stress response. Consequently the changes in STI and HI provide valuable information on SV adjustment during calibrated effort responses. Consequently, the changes in STI and HI, the relationship between STI and SV, and the study of SV, HR, and Q provide valuable information about the adjustment of these parameters during calibrated efforts.

scholarly journals Systolic Time Interval (STI) in Hypothyroid Patients Receiving High Dose L-Thyroxine

2020 ◽  
Vol 18 (2) ◽  
Author(s):  
Nurul Aulia Zakaria ◽  
Hafizah Pasi ◽  
Mohammad Arif Shahar
Keyword(s):  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Lv Function ◽  
High Dose ◽  
Time Interval ◽  
Ejection Time ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time ◽  
Significant Increment

Introduction: Systolic Time Interval (STI) is a simple,noninvasive and precise technique to assess left ventricular (LV) function. It measures aortic Pre-Ejection Period (PEP) over Left Ventricular Ejection Time (LVET) from echocardiogram. Thyrotoxicosis will enhance LV function and cause reduction of STI.  This study was perform to measure the changes of STI after administration of high dose L-thyroxine and to determine the correlation between high dose L-thyroxine administration and STI. Materials and Method: A Total of 22 patients were screened. Those with cardiac diseases and high Framingham risk score were excluded. Nine patients were started on high dose L-thyroxine (7x their usual dose) once a week during the month of Ramadan.Thyroid hormones ( T3,T4,TSH)  and STI (PEP/LVET) were measured at baseline and within 24 hrs after high dose L-thyroxine ingestion. Results: All patients have normal thyroid hormones level and normal cardiac function at baseline. The median dose (mcg) of L-thyroxine was 600 (437.5,700) while the median level of fT4 (pmol/L) was 17.43(12.38,20.8). Despite the significant increment of fT4 after Lthyroxine ingestion [baseline 13.21(8.19,14.63) vs high dose 17.43(12.38,22.55) p; 0.011] there was no significant change in STI [baseline 0.3(0.2,0.4) vs high dose 0.28(0.26,0.45) p; 0.513]. There was no correlation found between the dose of Lthyroxine and STI (r=0.244 , p;0.526).  Conclusion: Administration of high dose Lthyroxine did not significantly alter STI despite significant increment of fT4 level unlike the naturally occurring thyrotoxicosis.Therefore ‘exogenous’ administration of high dose L-thyroxine is cardiac safe.

scholarly journals A Close Examination of the Use of Systolic Time Intervals in the Calculation of Impedance Derived Cardiac Autonomic Balance and Regulation

2021 ◽  
Vol 15 ◽  
Author(s):  
Cameron R. Wiley ◽  
Vida Pourmand ◽  
Julian F. Thayer ◽  
DeWayne P. Williams
Keyword(s):  
Sympathetic Activity ◽  
Parasympathetic Nervous System ◽  
Left Ventricular ◽  
Left Ventricular Ejection ◽  
Future Research ◽  
Time Interval ◽  
Autonomic Balance ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time

Traditionally, impedance derived measures of cardiac autonomic balance (CAB) and regulation (CAR) are calculated using indices of heart rate variability (HRV) that primarily reflect parasympathetic nervous system activity (e.g., high-frequency HRV | HF-HRV) and pre-ejection period (PEP; a systolic time interval and measure of sympathetic activity). However, HF-HRV and PEP are considered measures of chronotropic and inotropic cardiac influence, respectively. Left ventricular ejection time (LVET) is a systolic time interval that reflects sympathetic chronotropic influence, and therefore may be a more appropriate measure for calculating CAB and CAR compared to PEP. Thus, the current study evaluates both PEP and LVET in the calculation of CAB and CAR. Data from 158 healthy participants (mean age = 19.09 years old, SD = 1.84 years) were available for analyses. CAB and CAR values were calculated using both HF-HRV and the root mean square of successive differences, in addition to both PEP and LVET, in accordance with previously established guidelines. Analyses showed that correlations were significantly weaker between CAB and CAR calculated using LVET for both HF (z = 5.12, p < 0.001) and RMSSD (z = 5.26, p < 0.001) than with PEP. These data suggest that LVET, compared to PEP, provides better “autonomic space” as evidenced by a lack of correlation between CAB and CAR computed using LVET. We stress that future research consider calculating CAB and CAR using chronotropic measures for both parasympathetic and sympathetic activity, as doing so may yield more accurate and independent measures of cardiac autonomic activity compared to a mixture of inotropic (i.e., PEP) and chronotropic (i.e., HF-HRV) measures.

Systolic Time Interval Characteristics in Children with Duchenne's Progressive Muscular Dystrophy

PEDIATRICS ◽  
1982 ◽  
Vol 70 (6) ◽  
pp. 958-964
Author(s):  
Shyamal K. Sanyal ◽  
Ralph C. Tierney ◽  
P. Syamasundar Rao ◽  
Samuel E. Pitner ◽  
Stephen L. George ◽  
...  
Keyword(s):  
Heart Rate ◽  
Muscular Dystrophy ◽  
Normal Control ◽  
Left Ventricular ◽  
Time Interval ◽  
Systolic Time Interval ◽  
Control Subjects ◽  
Systolic Time ◽  
Ventricular Ejection Time ◽  
Duchenne's Muscular Dystrophy

Systolic time interval (STI) characteristics of 17 boys with Duchenne's muscular dystrophy (DMD) were compared with those of 80 normal boys who served as control subjects. The heart rate decreased linearly with age in normal control subjects (r = -.47, P < .01). By contrast, heart rate was significantly higher in patients with DMD (P <.001) and tended to increase further with age. Each STI variable for normal control subjects increased significantly with age (P ≤ .01); QII, left ventricular ejection time (LVET), and pre-ejection period (PEP), in addition, decreased with increasing heart rate (P ≤ .05). In dystrophic patients QII and LVET decreased with increasing heart rate (P < .001) but were not influenced by age. None of the other STI values in dystrophic patients was significantly influenced by either age or heart rate. Mean QII, LVET, and QI were shorter and PEP, isometric contraction time (ICT), and PEP/LVET ratio were longer (P < .001) for DMD patients than for normal control subjects. In 13/17 patients, QII and LVET were below the 95% confidence interval of the normal mean, whereas PEP, ICT, and PEP/LVET exceeded the upper limits of normal in 8, 9, and 11 patients, respectively. For dystrophic patients, the difference (Δ) between the observed values and those predicted from regression equations for normal control subjects was lower for QII, LVET, and QI (P < .01) but higher for PEP (P < .04), ICT, and PEP/LVET ratio (P < .001). Δ QII and Δ LVET increased with age (P = .001 and .032, respectively). Duchenne's muscular dystrophy is thus documented to be associated with substantial alterations in STI characteristics that suggest a compromise of global left ventricular performance. Some of these abnormalities increase with age, probably reflecting the progressive cardiomyopathy characteristic of this disease.

Utility of M-Mode Echocardiography for Early Identification of Infants with Persistent Pulmonary Hypertension of the Newborn

PEDIATRICS ◽  
1981 ◽  
Vol 68 (4) ◽  
pp. 515-525 ◽  
Author(s):  
Lilliam M. Valdes-Cruz ◽  
Golde C. Dudell ◽  
Angelo Ferrara ◽  
Barbara J. Nickles
Keyword(s):  
Pulmonary Hypertension ◽  
Pulmonary Disease ◽  
Early Identification ◽  
Clinical Deterioration ◽  
Persistent Pulmonary Hypertension ◽  
Time Interval ◽  
Ejection Time ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Ventricular Ejection Time

The clinical syndrome of persistent pulmonary hypertension of the newborn (PPHN) still carries high mortality in spite of improved neonatal care. The purpose of this prospective study was to assess the utility of M-mode echocardiography for the early identification of infants with PPHN prior to clinical deterioration. Echocardiograms of 51 infants who needed fractional inspiratory oxygen (FIO2) ≥0.25 to maintain adequate Pao2 within 36 hours of life were compared to those of 115 healthy full-term and preterm newborns. Of the 51 infants, ten had elevated systolic time interval ratios of both ventricles simultaneously (ventricular pre-ejection period to ventricular ejection time [RPEP/RVET ≤0.50, LPEP/LVET ≤0.38J]). All of these newbrns had PPHN that was manifest clinically by 11 to 30 hours of age. The echocardiographic findings preceded clinical deterioration by at least one to five hours in all cases. The other 41 infants had clinical courses consistent with uncomplicated pulmonary disease. These data indicate that systolic time interval ratios, although not accurate measures of pulmonary arterial pressure and/or pulmonary vascular resistance, permit early identification of infants with PPHN and separation from others with uncomplicated pulmonary disease.

Neonatal Circulatory Changes: An Echocardiographic Study

PEDIATRICS ◽  
1977 ◽  
Vol 59 (3) ◽  
pp. 338-344
Author(s):  
Thomas Riggs ◽  
Stephen Hirschfeld ◽  
Connie Bormuth ◽  
Avroy Fanaroff ◽  
Jerome Liebman
Keyword(s):  
Right Ventricular ◽  
Systolic Time Intervals ◽  
Left Ventricular ◽  
Ventricular Ejection ◽  
Left Ventricular Ejection ◽  
Ejection Time ◽  
Time Intervals ◽  
Systolic Time ◽  
The Right ◽  
Ventricular Ejection Time

Serial echocardiograms were performed in the first three days of life on 38 normal full-term infants. Right ventricular systolic time intervals were measured from the pulmonic valve echogram and left ventricular systolic time intervals were determined from the aortic valve echogram. The heart rate, left ventricular pre-ejection period (LPEP), left ventricular ejection time (LVET), and LPEP/LVET ratio showed insignificant variation with increasing postnatal age. The right ventricular pre-ejection period (RPEP) shortened, the right ventricular ejection time (RVET) lengthened, and the RPEP/RVET ratio decreased with increasing age. The findings suggested that alterations in the RPEP/RVET ratio reflected the decreasing pulmonary artery diastolic pressure and pulmonary vascular resistance of the early neonatal period and may be valuable in the noninvasive evaluation of the newborn's pulmonary vascular bed.

Echocardiographic Characteristics of Premature Infants with Patent Ductus Arteriosus

PEDIATRICS ◽  
1983 ◽  
Vol 72 (6) ◽  
pp. 864-871 ◽  
Author(s):  
Gregory L. Johnson ◽  
Gerard L. Breart ◽  
Michael H. Gewitz ◽  
Joel I. Brenner ◽  
Peter Lang ◽  
...  
Keyword(s):  
Patent Ductus Arteriosus ◽  
Premature Infants ◽  
Aortic Root ◽  
Ductus Arteriosus ◽  
Left Ventricular ◽  
Time Interval ◽  
Systolic Time Interval ◽  
Systolic Time ◽  
Interval Ratio ◽  
Patent Ductus

As part of a multicenter collaborative study, M-mode echocardiograms were obtained shortly after birth on 3,559 premature infants with birth weight ≤1,750 g. Of these infants, 1,496 did not develop a cardiac murmur or other signs of a "hemodynamically significant" patent ductus arteriosus (PDA). Echocardiographic parameters from this "normal" group were compared with results obtained from 415 infants in whom PDA was diagnosed on the basis of clinical findings alone, irrespective of the echocardiogram (PDA group). The best discrimination between the two groups, when considering a single parameter, was provided by a left atrial to aortic root ratio (LA/AO) of 1.40, a left ventricular to aortic root ratio (LV/AO) of 2.10, or a left ventricular systolic time interval ratio (LPEP/LVET) of 0.27. Multivariate analysis demonstrated that better separation between the two groups occurred when the left atrial to aortic root ratio and the left ventricular systolic time interval ratio were considered jointly. Because of a large degree of overlap of all echocardiographic variables between the normal group and the group with PDA, the echocardiogram alone was not a good indicator of PDA. However, when used in conjunction with a priori estimates of the probability of PDA (based, for example, on birth weight and degree of respiratory disease), use of echocardiographic data was found to improve the detection of hemodynamically significant patent ductus arteriosus in premature infants.

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