Left Ventricular Systolic Time Intervals Research Articles

Significant coronary artery disease detected by amyl nitrite and systolic time intervals

The relation between changes in left ventricular systolic time intervals with amyl nitrite (AN) inhalation and the severity of coronary artery disease (CAD) was evaluated in 77 patients who underwent catheterization because of chest pain. In 25 subjects with normal coronary angiograms (control group), AN inhalation increased the ejection time (ET), shortened the prejection period (PEP) and increased the ET/PEP markedly. In the 52 patients with CAD (CAD group), the ET/PEP changed insignificantly after AN. The difference between the 2 groups was significant (p < 0.001). At cardiac catherization, the increase of left ventricular dP/dt after AN in the control group was significantly larger than that in the CAD group. Although a positive correlation between changes in ET/PEP with AN and ejection fraction at rest was noted in patients with 1-vessel CAD, no such correlation was noted in those with multivessel CAD. This suggests that factors in addition to pump function, such as the degree of CAD, influence the effect of AN inhalation on systolic time intervals. When an increase of less than 30% in ET/PEP occurs with AN Inhalation, the presence of significant CAD can be detected with a sensitivity of 92%, a specificity of 84% and the predictive value of 92%. The AN inhalation test is safe and simple, and thus could serve as a stress test for evaluating the presence and severity of significant CAD.

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)

LEFT VENTRICULAR SYSTOLIC TIME INTERVALS BY DOPPLER-COMPARISON WITH CAROTID PULSE METHOD

We compared left ventricular systolic time intervals (L STI's) derived from pulsed Doppler(D) and from conventional(C) carotid pulse tracing(CPT) and phonocardiography(PCG) in 24 subjects, aged 1.7 to 18.5 yrs, median=12.1 yr. Using the apical 2-chamber view, D frequency-time curves from the proximal ascending aorta were recorded simultaneously with CPT,PCG and ECG. L STI's from the D tracings were measured as follows: pre-ejection period (PEP)-beginning of QRS to onset of D systolic upstroke; ventricular ejection time(VET)-onset of D systolic upstroke to maximal end-systolic flow reversal. The difference in pulse transmission time between onset and end of systole resulted in a systematically shorter PEP and longer VET by C. C PEP was best predicted by the regression equation C PEP=1.03(D PEP)-14, and C VET by C VET=0.99(D VET)+8. The cumulative distribution of the error of the predicted values and correlation coefficients(r) using these formulae were:

Echocardiographic Characteristics of Premature Infants with Patent Ductus Arteriosus

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.

Left ventricular dysfunction in Rocky Mountain spotted fever.

Rocky Mountain spotted fever is a serious infectious disease that continues to occur with increasing incidence in various areas of the United States. A high case-fatality ratio (11%) persists in spite of availability of adequate chemotherapeutic agents, and the cardiac involvement may play an important role in the final outcome of some cases. To assess the effect of the disease on left ventricular function 13 patients underwent M-mode echocardiographic examination on admission to a children's hospital. Increased left ventricular dimension was found in 3 patients and decreased left ventricular shortening fraction in 9. Diminished mean velocity of circumferential fiber shortening and increased left ventricular systolic time interval ratios were found in 8 patients and increased mitral valve E point to ventricular septal separation in 9. One patient died and biventricular dilatation with diffuse myocarditis was seen at autopsy. Repeat echo examination was available in 11 patients at follow-up (mean 5 months). Abnormal E mitral point to ventricular septal separation remained in 4 patients and decreased left ventricular shortening fraction in 2. The long-term prognosis for this group is unknown. Myocardial involvement is frequently present in Rocky Mountain spotted fever; close monitoring and aggressive therapeutic approach are essential if the high case-fatality ratio is to be reduced.

DIGOXIN THERAPY AND LEFT VENTRICULAR PERFORMANCE IN PREMATURE INFANTS WITH PATENT DUCTUS ARTERIOSUS

Left ventricular systolic time intervals were assessed in 16 preterm infants with symptomatic left-to-right ductal shunts, before, during and after digoxin therapy. An intravenous loading dose of digoxin, 20 micrograms/kg, resulted in a serum digoxin concentration of 1.94 +/- 0.44 nmol/l (mean +/- 1 SD) but in no significant change in heart rate or systolic time intervals. Digoxin maintenance, 2.5 micrograms/kg/12 h, led 3-7 days later to serum concentrations of 2.57 +/- 1.06 nmol/l with an associated shortening of left ventricular ejection time (p less than 0.05) which probably reflected a reduced ductal shunt. Digoxin therapy was withdrawn after ductal closure. The terminal serum half-life was 87 +/- 17 h. Decreasing digoxin concentrations were associated with prolongation of left ventricular ejection time (p less than 0.01). Digoxin therapy did not seem to influence left ventricular systolic time intervals while ductal patency persisted. This may be attributed to limitations of the method or the left ventricle already working at its maximum.

Alcohol-induced congestive cardiomyopathy: an animal model.

In an effort to determine the effect of ethanol ingestion on myocardial function in the domestic turkey, a group of Nicholas birds were fed 5% ethanol (25% of calories) for the first 56 days of life and compared with control turkeys. At 28 and 56 days, noninvasive determination of the percentage change in left ventricular diameter, left ventricular systolic time interval, systemic blood pressure, and heart rate were done in each group. In addition, Ca2+ transport of the isolated cardiac sarcoplasmic reticulum and Na+, K+-stimulated ATPase activity of isolated cardiac sarcolemma were determined in control and alcohol fed birds at 28 and 56 days. Combined ventricular weight·body weight−1 was also determined at each age in both groups. At both 28 and 56 days the percentage change in left ventricular diameter for the alcohol fed turkeys was reduced to 65% of the control value (P 0.10). Ca2+ transport studies of the isolated cardiac sarcoplasmic reticulum revealed depressed Ca2+ uptake to 76% of the control values at both ages (P 0.10). Na+, K+-stimulated ATPase levels of the isolated cardiac sarcolemma was also similar in each group of turkeys at 28 days. However, at 56 days, Na+, K+-stimulated ATPase was reduced to 50% of the value obtained in the control birds (P<0.01). The findings of this study document that the domestic Nicholas turkey develops congestive cardiomyopathy secondary to the ingestion of a moderate quantity of ethanol over a short period of time. The physiological, morphological, and biochemical data are comparative to that found in man with alcoholic cardiomyopathy and suggests that this animal model may be useful in the study of the spectrum of this cardiac disease.

Cardiac effects of clomipramine treatment. ECG and left ventricular systolic time intervals.

ECGs and left ventricular systolic time intervals were studied in 26 patients suffering from major depressive disorder treated with clomipramine. ECGs did not show, with one exception, drug-induced changes. The ratio of pre-ejection period to left ventricular ejection time, both corrected for heart rate (PEPc/LVETc), presented no significant changes, as compared with initial findings, in the group of patients considered as a whole. 27% of patients, however, showed individual percent changes greater than 8%, both increases and decreases having been observed. Cardiac findings were in no way related to clomipramine plasma levels.

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.

Myocardial function in rocky mountain spotted fever: Echocardiographic assessment

Nine patients with Rocky Mountain spotted fever underwent M-mode echocardiographic examination. Increased left ventricular dimension was found in 2 patients and decreased left ventricular shortening fraction in 7. Diminished mean velocity of circumferential fiber shortening, increased left ventricular systolic time intervals ratio, and increased mitral valve E point to ventricular septal separation were found in 6 patients. One patient died and at necropsy diffuse myocarditis was present. Repeat echocardiographic examination was available in the remaining 8 patients at follow-up (mean 10 months). Abnormal E mitral point to ventricular septal separation remained in 3 patients and decreased left ventricular shortening fraction in 2; in 1 there was also increased left ventricular end-diastolic dimension. Thus abnormal left ventricular function and chamber enlargement are frequently present in patients with Rocky Mountain spotted fever.

Left ventricular systolic time intervals in preterm infants with patent ductus arteriosus.

Left ventricular systolic time intervals were recorded by a non-invasive technique, from the axillary artery, in 13 preterm infants with patent ductus arteriosus. At the onset of clinical symptoms, consistent with a large left-to right ductal shunt, the preejection intervals were shorter than in a control group of nine preterm infants without a patent ductus. The most pronounced difference was found in the shortening of the isovolumic contraction time, 10.7 msec in the ductus group compared with 22.4 msec in the control group. Ductal closure normalized the isovolumic contraction time to 22.1 msec. The very short preejection intervals, associated with a large ductal shunt, are suggested to reflect a combination of reduced aortic diastolic pressure and increased left ventricular filling pressure. In spite of increased volume load to the left ventricle there were no detectable changes in the systolic time intervals indicating impaired left ventricular function. The left ventricle seems to be competent to handle increased volume load in the presence of reduced afterload in preterm infants with symptomatic left-to right ductal shunts.

Assessment of left ventricular adaptation to extrauterine circulation.

Left ventricular systolic time intervals (STI) were recorded by non-invasive technique from the axillary artery in fifteen normal newborns from 10-15 min to 70-74 hours after birth. The observed changes in the different STI could almost entirely be related to changes in the isovolumic contraction time (ICT). At the early postnatal recording ICT was only 21.0 msec suggesting an enhanced left ventricular performance compared to prenatal observations. During the following hours ICT increased to 31.6 msec which in some infants may imply a reduced left ventricular performance. This is suggested to coincide with ductal closure.

The effect of alcohol on the circulatory system adaptation to physical effort.

XPERIMENTAL STUDIES on animals and ob ervations of ethanol-intoxicated patients show that alcohol decreases myocardial contractility (1-4). Nakano and Moore (5) suggest hat this effect is related to blood alcohol concentration (B^c) and alcohol's solubility in fat and the extent to which it combines with cell structures. It has been found (3) that isometric contraction is affected the most, especially the left ventricular rate of pressure change. However, other investigators (e.g., 6) believe the effect of alcohol on the myocardium to be indirect, via the vegetative system. Some evidence to that effect comes from the studies })f Webbet al. (7), who observed decreased myocardial contractility in animals following intravenous administration of ethanol and no such effect in isolated lung-heart preparations. According to Delgado et al. (1) and Horwitz et al. (2), ethanol has a strong direct depressive effect on the myocardium, whereas neuroregulative stimulation affects only the heart rate (Ha). The depressive effect of alcohol on myocardial contractility may be related to its toxic action on the myocardial cells (5, 8). Assuming that ethanol does have a depressive ffect on the resting heart muscle contractility, we thought it interesting to investigate whether exercise-induced adrenergic stimulation can mask or enhance it. We decided to study the effect of ethanol on the hearts of healthy men during physical exercise and recovery, taking advantage of the results of previous analyses of left ventricular systolic time intervals (LVSTIS).

Nulceoprotein changes in the hearts of cardiomyopathic turkeys.

The possible involvement of nuclear proteins in the pathogenesis of a spontaneously occurring model of congestive cardiomyopathy in turkeys was examined. This model is characterised by cardiac hypertrophy and dilatation, reduced cardiac output and depressed contractility. The protein composition of myocardial nuclei was compared in normal (n = 9) and cardiomyopathic (n = 18) turkeys, 70 to 140 days old. Myopathic hearts as a group have a higher histone content (1.75 +/- 0.09 (SD) mg . mg DNA-1 vs 1.65 +/- 0.07 in controls, P less than 0.01) and histone/nonhistone protein (NHP) ratio (1.07 +/- 0.07 vs 0.95 +/- 0.02 in controls, P less than 0.01). The latter was independent of age and correlated well with the degree of cardiac dilatation. The electrophoretic patterns of chromatin proteins was decreased in myopathic hearts. This decrease was primarily accounted for by lower NHP phosphorylation (5.78 +/- 1.38 pmol 32P . mg prot-1 . 15 min-1 vs 8.33 +/- 0.81 in controls, P less than 0.01). DEAE-Sephacel chromatography separated cyclic AMP-dependent and -independent nuclear protein kinases with similar substrate specificities but lower specific activities in myopathic hearts. SDS-polyacrylamide similar substrate specificities but lower specific activities in myopathic hearts. SDS-polyacrylamide gel electrophoresis of phosphorylated nucleoproteins revealed differences in the lower molecular species of NHPs between control and myopathic hearts. There was a significant correlation between NHP phosphorylation and degree of cardiac dilatation (r = -0.78) or contractility as reflected by left ventricular systolic time intervals (r = -0.57). These results suggest that development of this model of spontaneous cardiomyopathy is associated with, and may, in part, be secondary to changes in the composition and function of myocardial nucleoproteins.

Mechanocardiographic assessment of systolic time intervals in normal children.

Systolic time intervals (STI) were measured in 469 normal children, aged 5.0 to 16.9 years, using simultaneous recordings of the electrocardiogram, phonocardiogram and an external carotid pulse tracing. The data were analyzed to define the influence of sex, age, cardiac cycle length, body weight (BW), body length (BL), and body surface area (BSA) on the left ventricular STI. Regression, equations were evaluated for the calculation of normal standards for the following STI: electromechanical systole (QS2), left ventricular ejection time (LVET), pre-ejection period (PEP) systolic quotient (PEP/LVET), isovolumic contraction time (IVCT), electroacustical delay (QS1), and additionally for the so-called tension time (TT), upstroke time (UT), and the ascending index (UT/LVET) of the carotid pulse wave. Heart rate was found to influence all of the STI but the ratio UT/LVET, which revealed to be independent of any variable. Besides heart rate, BSA proved to be a second relevant independent variable for QS2 and LVET, respectively BL for PEP, PEP/LVET and QS1. These findings are in accordance to the results of comparable echocardiographic studies but disagree previous mechanocardiographic studies in smaller groups of children in whom age and not the above-mentioned parameters of the individual development seemed to influence the STI. A second set of equations was evaluated for the calculation of 95%-prediction intervals for the particular STI permitting to define abnormalities of the STI in individual children.

130 NUCLEOPROTEIN COMPOSITION OF THE HEART OF THE CARDIOMYOPATHIC TURKEY

We examined the possible involvement of nuclear proteins in the pathogenesis of a naturally occurring model of congestive cardiomyopathy(CCM) in turkeys. The protein composition of myocardial nuclei was compared in CCM (n=18) and control (n=9) turkeys, 70-140 days old. CCM hearts as a group had a higher histone content (1.75±0.09(SD) mg/g vs 1.65±0.07 in Con, P<0.01) and histone/non-histone protein ratio (1.07±0.07 vs 0.95±0.02, P<0.01). The latter was independent of age and correlated well (r=0.89) with the degree of cardiac dilation. The electrophoretic pattern of chromatin proteins did not differ in the two experimental groups. In vitro phosphorylation of nuclei was decreased in CCM hearts (9.7± 0.2 vs 12.8±0.1 pmole32/mg prot/15 min, P<0.01). The decrease was due to lower NHP phosphorylation (5.78±1.38 vs 8.33±0.81 pmole 32P/mg prot/15 min, P<0.01). DEAE-Sephacel chromatography separated cyclic AMP-dependent and independent nuclear protein kinases. Lower cAMP-independent activities were present in CCM hearts. There was a significant linear correlation between NHP phosphorylation and degree of cardiac dilation (r=0.75) or contractility as reflected by left ventricular systolic time intervals (r=0.79). SDS-polyacrylamide gel electrophoresis of phosphorylated nucleoproteins revealed differences in the lower molecular weight species of NHPs between control and CCM hearts. These results suggest that development of this cardiomyopathy is associated with, and may be secondary to, changes in the composition and function of myocardial nucleoproteins.

1282 EFFECT OF CONSTANT DISTENDING PRESSURE (CDP) ON CARDIAC FUNCTION IN NEWBORN INFANTS

The cardiac function of 11 newborn infants (mean gestational age 34 ± 3 weeks and mean birth weight 2500 ± 780 g) requiring CDP for respiratory distress was serially assessed by M mode echocardiogram prior to CDP and 1/2 hour after establishment of CDP at ± 5 cm of H2O. Six infants received constant negative pressure (CNP) and 5, constant positive airway pressure (CPAP). There were no significant changes in stroke index, left ventricular systolic time intervals, left atrium/aortic ratio, ejection fraction, and % dimension change of the left ventricle, with changes in CDP. The ratio of right ventricular preejection period to eject time (RVPEP/RVET) was constantly decreased after introduction of CDP, more so with CNP than with CPAP (0.49 ± 0.11 to 0.35 ± 0.07 after CNP, p<0.01; 0.45 ± 0.10 to 0.34 ± 0.01, after CPAP, p<0.05). Cardiac index decreased after CNP (1.98 ± 0.79 to 1.16 ± 0.50, p<0.05) but did not change after CPAP (1.38 ± 0.14 to 1.58 ± 0.52 p<0.9). PaO2 increased after both CNP and CPAP (61 ± 13 to 92 ± 22 after CPAP, p<0.01; 58 ± 9 to 82 ± 13 after CNP p<0.02). These results suggest that the increased PaO2 after CDP decreases pulmonary resistance as measured by RVPEP/RVET. Other parameters of mycocardial function are unaffected by CDP at a level of ± 5 cm of H2O.

Left ventricular function in patients with chronic obstructive pulmonary disease.

We assessed the left ventricle function in 24 patients with severe (forced expiratory volume in 1 sec less than 50% of predicted) chronic obstructive pulmonary disease (COPD) and in 21 normal people. We measured the left ventricular systolic time intervals (STI) and echocardiographic left ventricular diameters, volumes, cardiac index, stroke volume index, echo ejection fraction and functional mean rate of circumferential fiber shortening (Vcf). In 13 of the 24 patients with COPD the mean pulmonary artery pressure and pulmonary artery wedge pressure were recorded. The STI in the patients with COPD were found abnormal while the echocardiographic parameters and pulmonary wedge pressure were normal. 1 patient had a high pulmonary arterial wedge pressure and a low Vcf. 2 patients had an ejection fraction less than 60%, but in only 1 of these the Vcf was low. No patient had all three parameters abnormal. We conclude that in patients with COPD the increased right ventricular afterload and the interaction between left and right ventricles are responsible for the abnormal left ventricular STI, while the left ventricular function is normal.

Perioperative echocardiographic evaluation of cardiovascular function: assessment of changing hemodynamic state.

To evaluate echocardiographic assessment of ventricular function in a changing hemodynamic situation, 20 infants and children undergoing open heart surgery were examined preoperatively and 1,4 and 24 hours postoperatively by this technique. Clinical evaluation and measurements of cardiac output were obtained simultaneously with each echocardiogram. On the basis of their clinical course and cardiac output, the patients were divided into two groups: group 1 - cardiac index > 2.3 1/min/m2 without inotropic support (n = 9); and group 2 - cardiac index less than or equal to 2.3 1/min/m2 and/or need for inotropic support (n = 11). Of the echocardiographic measurements obtained, the left ventricular systolic time interval ratio (left ventricular preejection period/left ventricular ejection time ([LVPEP/LVET] correlated significantly with the clinical course, separating the two groups of patients completely at each determination. The aortic root velocity (AoV), a new index defined as the anterior excursion (in degrees) of the aortic root from the horizontal plane with systole, also correlated with the clinical course, although this was not statistically significant. Serial change in LVPEP/LVET and AoV crrrelated with changes in clinical status and cardiac output for individual patients. Using a formula based on the opening slope of the mitral valve, echocardiographic estimations of cardiac output correlated well with those determined by dye dilution. The results indicate that selected echocardiographic indexes can be used for serial assessment of cardiac performance in patients with a changing hemodynamic state.

Normal Pulmonary Vascular Resistance and Left Ventricular Hypertrophy in Young Infants with Bronchopulmonary Dysplasia: An Echocardiographic and Pathologic Study

To evaluate the cardiac anatomy and functional hemodynamics in young infants with chronic lung disease, nine patients, aged 2 to 7 months, with a clinical diagnosis of bronchopulmonary dysplasia (BPD) underwent echocardiographic examination. All infants required supplemental O2 (mean FIO2 35%) to maintain adequate systemic oxygenation (Pao2 greater than 50 mm Hg). None of the infants had evidence of a patent ductus arteriosus at the time of examination. Echocardiographic measurements of left and right ventricular systolic time intervals revealed normal systolic time interval ratios suggesting pulmonary vascular resistances. However, echocardiographic evidence of left ventricular hypertrophy was found in eight of the nine infants, while right ventricular anterior wall thickness and right ventricular diastolic dimensions were not increased. Two infants died; marked left ventricular hypertrophy was noted at the time of postmortem examination while the right ventricular wall thickness was normal. The findings of left ventricular hypertrophy led to a retrospective review of autopsy material of seven patients who died with BPD over the past year. In six of seven cases examined, left ventricular posterior wall thickening was noted (range 7 to 11 mm); while the right ventricular wall thickness was normal (range 2 to 5 mm). These data suggest that (1) as assessed by echocardiography, the pulmonary vascular resistance is not significantly elevated in young infants with BPD, and (2) a hypertrophic left ventricle evolves which may assume importance in the pathogenesis of pulmonary edema in BPD, though the precise etiology remains undetermined.