Isovolumic relaxation time in normal subjects and patients with cardiac disease: comparison of determinations made with echocardiographic techniques and apex cardiography

B-type natriuretic peptide and echocardiography reflect volume changes during pregnancy

OBJECTIVE

To evaluate B-type natriuretic peptide (BNP) and N-terminal pro-B-type natriuretic peptide (NT-proBNP) and cardiac structure and function in normal women through pregnancy and the postpartum.

METHODS

In this prospective observational study, we obtained serial transthoracic echocardiograms, BNP, and NT-proBNP at seven intervals from 6 weeks' gestation through 12 months postpartum. Women with hypertension or cardiac disease were excluded. Using 6-12 months postpartum as reference for non-pregnant levels, echocardiogram measurements and BNP/NT-proBNP were compared over time using linear mixed models with Tukey-Kramer adjustment for multiple comparisons.

RESULTS

Of 116 patients, data was available for 78-114 healthy pregnant or postpartum women within each time interval, and 102 patients provided data for ≥4 intervals. Compared to 6-12 months postpartum, BNP and NT-proBNP remained stable through pregnancy and delivery, increased within 48 h postpartum (P<0.0001), then returned to baseline. Left ventricular volume increased within 48 h postpartum (P=0.021) while left atrial volume increased at 18-24 weeks (P=0.0002), 30-36 weeks (P<0.0001) and within 48 h postpartum (P=0.002). The transmitral early/late diastolic velocity (E/A) ratio, transmitral early/peak mitral annulus diastolic velocity (E/E') ratio, isovolumic relaxation times, and mitral valve deceleration times were similar within 48 h and 6-12 months postpartum.

CONCLUSION

In normal women, BNP/NT-proBNP, left atrial, and left ventricular volumes increase within 48 h postpartum without indications of altered diastolic function.

The apical impulse in coronary heart disease

Forty patients (36 with coronary artery disease), who had angiographic assessment of left ventricular function were studied using apexcardiography with a new method of standardization, the objective being to define the parameters of the apical impulse which reflect changes in the left ventricular function and correlate them with clinical assessment of the apical impulse. Based on measurements from patients with normal left ventricular function, abnormalities in apexcardiograms were identified. An increase in amplitude of percent A wave alone (greater than 13.3%) (palpable as an atrial kick in approximately half of these patients) was not associated with significant left ventricular dysfunction. An isolated abnormality in isovolumic slopes, although associated with mild left ventricular dysfunction, could not be detected clinically. Moderate to severe left ventricular dysfunction was always associated with abnormal ejection phase slopes and all had sustained apical impulses. The additional presence of a palpable atrial kick or an increased percent A wave on the apexcardiogram was more indicative of moderate rather than severe dysfunction. Thus this study clearly establishes that left ventricular function does in fact affect the nature of the apical impulse in patients with coronary artery disease and these can be easily defined.