Abstract 3756: The Fourth Heart Sound is Associated with Increased Left Ventricular End-Diastolic Elastance
Background: The significance of the fourth heart sound (S4) is unclear. Although the S4 is thought to be associated with a stiff ventricle, prior studies have failed to consistently show an association between abnormal diastolic hemodynamics and the S4. Recently, single-beat estimation of the end-diastolic pressure volume relationship (EDPVR) has been characterized (P = αVβ), allowing measurement of EDPVR in larger numbers of patients.
Hypothesis: The S4 is associated with an upward- and leftward-shifted EDPVR, indicative of elevated end-diastolic elastance (stiffness).
Methods: Within a 4-hour period, 90 subjects underwent computerized phonocardiography, echocardiography, and left heart catheterization. In each patient, we calculated α and β coefficients to define the non-linear slope of the EDPVR using the single-beat method.
Results: The mean age was 62±14 years, 65% were male, 36% had heart failure, and 67% had coronary disease. Phono detected an S4 in 29 patients (32%). S4 patients were older (p=0.048), but were otherwise similar in demographic and clinical characteristics to those without S4. On echo, subjects with an S4 had a trend towards lower LVEF (59.9 ± 17.6 vs. 51.8 ± 20.0, p=0.076), and had higher end-diastolic (p=0.003) and end-systolic (p=0.007) volumes. However, there were no differences in mitral inflow characteristics, though tissue Doppler E/E’ (p=0.04) was higher in the S4 group. On invasive hemodynamics, the peak (p=0.0006) and height (p=0.0002) of the A wave in the LV diastolic pressure tracing was significantly higher in the S4 group. In the P = αVβ EDPVR estimation, α was similar (p=0.31) but β was higher in the S4 group (5.96 ± 0.53 vs. 6.51 ± 0.94, p=0.002), signifying a steeper, left-shifted EDPVR curve in the S4 patients. The intensity of the S4 was associated with both β (r=0.42, p < 0.0001) and E/E’ χ stroke volume, another measure of diastolic stiffness (r=0.39, p=0.0008). On multivariable analysis, βremained associated with the presence (p=0.008) and intensity (p<0.0001) of S4 after controlling for age, sex, and LVEF.
Conclusions: The S4 is most likely due to a high pressure A wave at end-diastole, coupled with an abnormally stiff ventricle. These findings support the notion that the S4 is a pathologic finding in older patients.