Right Ventricular Systolic Time Intervals Research Articles

Right Ventricular Systolic Function Is Not Depressed In Morbid Obesity

The increased pulmonary blood volume associated with the increased total blood volume in morbidly obese patients increases pulmonary artery pressure and pulmonary vascular resistance, resulting in increased right ventricular (RV) afterload. Thus, the morbidly obese may develop RV dysfunction owing to the increased RV afterload. We examined this possibility by assessing RV contractile function in morbidly obese patients, using RV end-systolic pressure-volume relationship and RV systolic time intervals. Included were 25 morbidly obese patients undergoing gastric bypass surgery under general anesthesia. Pulmonary artery pressure and RV end-systolic volume were measured with a thermodilution pulmonary artery catheter. Pulmonary arterial dicrotic notch pressure was used as an estimate of RV end-systolic pressure. Two data points were used to define RV end-systolic pressure-volume relationship. RV systolic time intervals were determined by simultaneous graphic display of the electrocardiograph, phonocardiograph, and pulmonary artery pressure curve, and were expressed as a pre-ejection period/RV ejection time ratio. The mean slope of right ventricular end-systolic pressure-volume relationship line was 0.54 +/- 0.13 and mean pulmonary vascular resistance 274 +/- 80 dyne.sec.cm(-5).m(-2). The mean pre-ejection period/RV ejection time ratio was 0.4 +/- 0.11. There was an inverse correlation between the pre-ejection/RV ejection time ratio and the slope of RV end-systolic pressure-volume relationship line (R(2)=0.658, P<0.0001). Our data indicate that RV function is not depressed in morbid obesity despite increased RV afterload.

Effect of patent ductus arteriosus on Doppler-derived right ventricular systolic time intervals.

Right ventricular systolic time intervals (RVSTI) and noninvasive Doppler-derived pulmonary blood flow were measured before and after surgical ductus ligation in 18 otherwise healthy infants and children who were older than 3 months of age. Right ventricular preejection period (PEP) and the ratio of preejection period and right ventricular ejection time (PEP/RVET), both corrected or uncorrected for heart rate, decreased significantly following surgery (PEP 71 +/- 14 vs. 50 +/- 13, p < 0.001 and PEP/RVET 0.29 +/- 0.06 vs. 0.21 +/- 0.05, p < 0.001). The volume of pulmonary blood flow correlated with PEP/RVET (r = 0.48, p = 0.003). The magnitude of the change in pulmonary blood flow correlated with the change in PEP/RVET (r divided by 0.56, p = 0.016). The velocity of circumferential fiber shortening (VCFc) increased after surgery, but not significantly. We speculate that patent ductus arteriosus has a similar effect on right ventricular performance when other congenital heart defects are present.

Long-term follow-up of right ventricular function after Mustard operation for transposition of the great arteries.

As development of right ventricular (RV) failure is a potential risk after Mustard operation for transposition of the great arteries, 17 patients were reexamined 5-13 years postoperatively. Comparisons were made with healthy controls. There were no clinical signs of heart failure. Echocardiographically determined RV end-diastolic diameter was increased to 2.5 +/- 0.8 cm (controls: 1.5 +/- 0.4 cm, p less than 0.001). Comparison of RV systolic time intervals (STI) in patients with normal left ventricular (LV) STI revealed decreased RV function, with RPEPI 165 +/- 19 msec (controls 126 +/- 12, p less than 0.001) and RPEP/RVET 0.484 +/- 0.096 (controls 0.284 +/- 0.045, p less than 0.001). Nuclear angiography demonstrated decreased RV ejection fraction (EF), viz. 42.8 +/- 6.6% (normal RV 53 +/- 6%, LV 68 +/- 9%, p less than 0.001). Only two patients showed normal (5%) rise in RV-EF during exercise. There was no evidence of deterioration with passage of time. The results do not justify use of anatomic repair at our center, since the perioperative mortality might then be higher than in the Mustard or Senning procedures.

Comparison of Doppler-determined elevated pulmonary arterial pressure with pressure measured at cardiac catheterization

This study assesses use of pulsed Doppler echocardiography to measure pulmonary artery (PA) pressure. PA flow at the right ventricular (RV) outflow tract was analyzed in 51 patients. Attention was focused on PA flow morphologic pattern, RV systolic intervals, time to peak flow and acceleration time index. Correlation was made with PA pressure and total pulmonary resistance. Three morphologic patterns of PA flow were found: type I indicates normal PA pressure (sensitivity 85%, specificity 100%) and types II and III indicate PA hypertension (sensitivity 100%, specificity 85%). The RV preejection/RV ejection ratio, time to peak flow and acceleration time index show a good correlation coefficient improved when a logarithmic function was applied. The best correlation was achieved with time to peak flow (r = −0.77 with PA pressure, r = −0.79 with total pulmonary resistance), and especially with acceleration time index (r = −0.84 with PA pressure, r = −0.87 with total pulmonary resistance). Analysis of pulmonary flow is a reliable new tool for evaluating PA pressure and is even better for evaluating total pulmonary resistance. Acceleration time index is the parameter that correlates best with these 2 variables.

Clinical and echocardiographic evidence suggesting afterload reduction as a mechanism of action of tolazoline in neonatal hypoxemia.

The effect of tolazoline was assessed in 29 hypoxic neonates. Tolazoline was given in a bolus starting at 1 mg/kg and repeated or infused for 5-134 hours. A "good clinical response," defined as a rise in PaO2 of more than 20 mm Hg, was obtained in 23 (79%), 20 of this group were weaned from the respirator, and three died. Six infants did not respond initially and four died. Failure to respond to tolazoline or to be weaned from the ventilator was usually associated with severe additional pathology. Urine output (greater than 1 ml/kg/h) was adequate in most neonates during therapy. In those with preexisting oliguria (less than 1 ml/kg/h), output improved during therapy. Blood pressure monitoring showed a fall in blood pressure in 19 patients during tolazoline administration, but true hypotension only occurred in four; in seven there was no fall and in three there was a rise in blood pressure. Echocardiography was performed prior to therapy in 19 patients and repeated in 12 patients after 24 h. Additional "tracking" was performed at 10 min, 1 h, and 4 h in seven patients. Prior to therapy, right ventricular dysfunction was demonstrated by abnormal right ventricular systolic time intervals (RVSTIs) in 17 of the patients tested. A rapid improvement was evident during therapy especially with "tracking." Left ventricular dysfunction, assessed by left ventricular systolic time intervals (LVSTIs), ejection fraction (EF), shortening fraction (SF), and velocity of circumferential fiber shortening (VCF), was also evident prior to therapy and improved, though more gradually than the RVSTIs.(ABSTRACT TRUNCATED AT 250 WORDS)

Initial systolic time intervals as predictors of the severity of transient tachypnea in term neonates.

42 term neonates with transient tachypnea (TTN) underwent echocardiography and determination of systolic time intervals before the age of 4 hours. Based on initial measurement of right ventricular systolic time intervals (RVSTIs) the patients were divided in two groups: neonates with RVSTI ratios less than or equal to 0.50 (Group I) (n = 35) and neonates with RVSTI ratios greater than 0.50 (Group II) (n = 7). Group II neonates also had significantly more prolonged left ventricular systolic time intervals (LVSTIs) than Group I neonates. Group II neonates developed markedly more severe form of TTN than Group I neonates. Initially prolonged RVSTI was best predictor of the development of severe TTN (relative risk ratio 17.5, p less than 0.001): clinical characteristics and oxygen requirements at the admission had limited predictive value.

Assessment of the pulmonary vascular bed by echocardiographic right ventricular systolic time intervals.

Echocardiography was used to measure right ventricular systolic time intervals (RVSTI) in 85 normal children (group I) and in 229 patients undergoing cardiac catheterization (group II). Corrected right ventricular pre-ejection period (RPEPC) and right ventricular ejection time (RVETc) (based on regression analysis of group I) and RPEP/RVET were each correlated with pulmonary artery (PA) diastolic and mean pressures and pulmonary vascular resistance (PVR). The best correlation (0.83) was between a second degree polynomial of the RPEP/RVET and PA diastolic pressure. The RPEP/RVET allowed prediction of PA diastolic pressure within 10 mm Hg in 85% of the patients. The utility of RPEP/RVET was confirmed in sequential data of 22 patients, in whom alteration in RPEP/RVET accurately reflected the changing PA diastolic pressure. The RPEP/RVET could not be used to assess PA pressure in six patients with congestive cardiomyopathy nor in 18 patients with complete right bundle branch block (CRBBB).

The echocardiographic assessment of pulmonary artery pressure and pulmonary vascular resistance.

Serial assessment of the status of the pulmonary vascular bed requires bed requires cardiac catheterization. We have demonstrated the right ventricular systolic time intervals (RVSTI) may be measured from the pulmonary valve echo. The right ventricular ejection time (RVET) and right pre-ejection period (RPEP) were measured in 45 normal patients. The RVET and RPEP decreased with increasing heart rate but increased with age. The RPEP/RVET, however, was uninfluenced by either age or heart rate. The RPEP/RVET was, therefore, determined from the pulmonary valve echo in 64 patients with congenital heart disease who underwent cardiac catheterization. Increased pulmonary artery diastolic pressure (PADP), pulmonary vascular resistance (PADP), pulmonary vascular resistance (PVR) and mean pulmonary artery pressure (MPAP) resulted inan increased RPEP/RVET. The use of the RPEP/RVET permitted the serial echographic evaluation of the pulmonary vascular bed in selected patients; marked elevation of the ratio indicated the presence of pulmonary hypertension.