Transient Pulsus Alternans After PVC in Heart Failure
Patients with heart failure develop transient pulsus alternans after a PVC because the post-extrasystolic potentiation (PESP) causes an alternating pattern of left ventricular contractility that becomes visible as alternating pulse pressures, particularly when the ratio of arterial elastance to ventricular contractility (Ea/Emax) is elevated—a hallmark of failing hearts.
Mechanism Explained
The phenomenon occurs through a specific physiological sequence:
Post-Extrasystolic Potentiation Creates Contractility Alternans
After a PVC, the compensatory pause allows increased ventricular filling, leading to PESP. The key finding is that left ventricular contractility (Emax) decays in a transient alternating pattern—not exponentially—during PESP 1. This means the first post-PVC beat is strong, the second is weak, the third is strong again, and so on for several beats.
Why It's Visible in Heart Failure
The critical insight is that this contractility alternans occurs in both normal and failing hearts, but only becomes clinically apparent as pulsus alternans when the Ea/Emax ratio is high 1. In heart failure:
- Elevated afterload (high Ea) combined with reduced contractility (low Emax) creates a high Ea/Emax ratio
- This high ratio amplifies the alternating contractility pattern into visible pulse pressure alternations
- In normal hearts with lower Ea/Emax ratios, the same contractility alternans occurs but is masked and doesn't manifest as detectable pulsus alternans 1
Hemodynamic Factors
The occurrence and severity depend on:
- Duration of systole of the first strong post-PVC beat 2
- Rate of rapid diastolic filling of the second weak beat 2
- Heart rate—the pressure of the second post-PVC beat augments up to 120 bpm, then decreases approximately 10 mmHg for each 10 bpm increase 2
Clinical Context
Patient Characteristics
Patients who develop pulsus alternans after PVCs typically have 3:
- Older age
- Higher left ventricular end-diastolic pressures (17±9 vs 13±6 mmHg)
- Lower ejection fractions (0.42±0.13 vs 0.53±0.14)
- Higher pulmonary artery systolic pressures
- Valvular heart disease (particularly aortic stenosis)
Important caveat: 28% of patients with inducible pulsus alternans may have normal ejection fraction (>0.50) and normal LVEDP (<13 mmHg) 3, so this finding doesn't exclusively indicate severe systolic dysfunction.
Prognostic Significance
The presence of pulsus alternans, whether spontaneous or post-PVC, indicates significant cardiac compromise 4, 5. Echocardiographic detection of Doppler alternans may precede clinical signs, allowing timely escalation of care 5.
Clinical Recognition
Echocardiography is essential for accurate assessment 6. Key parameters to evaluate:
- LVOT-VTI variation between strong and weak beats (∆LVOT-VTI ranges 19-52% in PA patients) 6
- Global longitudinal strain (GLS) is significantly reduced (range -1.2% to -10.4%) 6
- Peak strain dispersion (PSD) is increased (47-117.5 ms) 6
- Strong correlations exist between hemodynamic parameters and GLS 6
Common Pitfall
Don't rely solely on arterial pressure or LVP monitoring—these can illude the underlying contractility alternans in patients without severe heart failure 1. The alternating contractility pattern may be present but not visible on standard pressure tracings in less severe cases.