Pulsus alternans is a clinical sign characterized by a beat-to-beat alternation in the strength and amplitude of the peripheral arterial pulse while the rhythm remains regular. It is a hallmark of severe left-sided heart failure and may be accompanied by changes in the intensity of heart sounds or pre-existing heart murmurs.

Pulsus alternans reflects fluctuations in stroke volume due to alternating contractility of the left ventricle. Though it is most often associated with heart failure, it can rarely appear in patients with normal ventricular function, but usually only transiently.

Pathophysiology

• Alternating left ventricular contractility: Strong and weak contractions occur in succession, producing corresponding variations in peripheral pulse amplitude.

• Hemodynamic consequences: Recumbency or exercise increases venous return, temporarily normalizing the pulse. Successful treatment of heart failure resolves the abnormal pulse.

• Detection threshold: A difference in systolic pressure exceeding 20 mm Hg between consecutive beats is considered clinically significant.

Detection

• Palpation: Radial, brachial, or femoral arteries may reveal alternating strong and weak pulses. Breath-holding during palpation reduces interference from respiratory-induced pressure changes.

• Sphygmomanometry: Inflate cuff 10–20 mm Hg above systolic pressure, then slowly deflate. Initially, only strong beats are audible; all beats become perceptible as cuff pressure decreases. The peak-to-average difference estimates the degree of pulsus alternans.

• Total pulsus alternans: When the weak beat is not palpable, peripheral pulse appears halved relative to the actual heart rate.

Emergency interventions

Pulsus alternans signals critical cardiac compromise:

• Rapidly assess vital signs: blood pressure, heart rate, respiratory rate, oxygen saturation

• Auscultate for ventricular gallop and pulmonary crackles

• Ensure airway and oxygenation are adequate

• Prepare for immediate transfer to an intensive or cardiac care unit if left-sided heart failure is acute

• Consider pulmonary artery catheterization for hemodynamic monitoring

Medical Causes

Special considerations

• Elevate the head of the bed to improve respiratory excursion and oxygenation

• Adjust therapy to optimize cardiac output, reduce cardiac workload, and promote diuresis

• Monitor for sudden decompensation, especially if patient develops acute pulmonary edema

Patient counseling

• Educate about left-sided heart failure and its progression

• Review prescribed medications, expected benefits, and potential adverse effects

• Stress lifestyle modifications (sodium restriction, fluid management, activity pacing)

• Emphasize importance of regular follow-up and adherence to treatment

Pediatric pointers

• Pulsus alternans may also occur in children with heart failure

• Assessment can be difficult if the child is crying or restless; soothing measures (holding or gentle comfort) may facilitate evaluation

References

1. Buttaro TM, Tybulski J, Bailey PP, Sandberg-Cook J. Primary care: A collaborative practice. St. Louis (MO): Mosby Elsevier; 2008. p.444–447.

2. Sommers MS, Brunner LS. Pocket diseases. Philadelphia (PA): F.A. Davis; 2012.

3. McCance KL, Huether SE, Brashers VL, Rote NS. Pathophysiology: The biologic basis for disease in adults and children. 7th ed. Maryland Heights (MO): Mosby Elsevier; 2014.

4. Goldberger ZD, Bonow RO, Mann DL, Zipes DP. Braunwald’s heart disease: A textbook of cardiovascular medicine. 12th ed. Philadelphia (PA): Elsevier; 2021.

5. Lilly LS. Pathophysiology of heart disease: A collaborative project of medical students and faculty. 6th ed. Philadelphia (PA): Wolters Kluwer; 2016.St. Louis, MO: Elsevier; 2019.