Pulsus Alternans: Explained

Pulsus alternans is a physical finding characterized by a regular heart rhythm accompanied by alternating strong and weak pulse amplitudes. In other words, although the heart rate remains constant, the force of ventricular contraction—and consequently the stroke volume—varies from beat to beat. This variation is most often indicative of severe left ventricular systolic dysfunction, such as that seen in advanced heart failure or cardiomyopathy.

Causes of pulsus alternans

Pulsus alternans occurs as a result of underlying cardiac distress and dysfunction. It is a symptom of these conditions. 

Pulsus alternans can be grouped into three different types depending on which of the two ventricles are affected: left ventricular alternans, right ventricular alternans, and biventricular alternans (both ventricles). These different variations of pulsus alternans are associated with different conditions.

Left ventricular alternans

Left ventricular alternans is the most common type of pulsus alternans and occurs when you have severe left ventricular dysfunction (or left-sided heart failure). This could be caused by:

• Cardiomyopathy
• Coronary artery disease (CAD)
• Aortic stenosis
• Systemic hypertension (high blood pressure)

Right ventricular alternans

Right ventricular alternans occur when you have right ventricular strain or dysfunction (or right-sided heart failure). This could be caused by:

• Pulmonary embolism
• Pulmonary hypertension (high blood pressure)
• Reactive airway disease or asthma
• Mitral stenosis
• Left-sided heart failure

Biventricular alternans

Biventricular alternans is a very rare form of pulsus alternans where both of the ventricles are affected. The cause is not fully understood. It has been reported in cases of:

• Severe left ventricular dysfunction
• Left anterior descending coronary artery disease

How can pulsus alternans be treated?

Given that pulsus alternans is a sign of underlying cardiac dysfunction or disease, treatment involves the management of the underlying pathology. For example, this might include:

• Heart-failure medication (e.g. diuretics, ACE inhibitors, digitoxin) for left-sided heart failure
• Medication (e.g. antihyperlipidemic drugs, aspirin, beta-blockers) or surgery for coronary artery disease
• Aortic valve replacement for severe aortic stenosis
• Medication (e.g. anticoagulant medicines, diuretics, digoxin) or oxygen therapy for pulmonary hypertension
• Anticoagulant medication (blood thinners) or thrombolytic medication for a pulmonary embolism 

Pathophysiology

The underlying mechanism is thought to be related to the heart’s contractile variability. In a failing left ventricle, the reduced ability to generate a consistent contraction can lead to alternating strong and weak beats. One explanation is that after a weak contraction (with low stroke volume), the remaining blood volume in the ventricle increases the end-diastolic volume. This elevated volume, via the Frank–Starling mechanism, leads to a compensatory stronger subsequent contraction. Conversely, the beat following this strong contraction may suffer from suboptimal filling, resulting in a weaker subsequent contraction .

Another perspective involves the heterogeneity in the myocardial cells’ refractory periods, where differences between healthy and diseased regions of the myocardium contribute to this alternating pattern.

Clinical Evaluation and Significance

• Detection: Clinically, pulsus alternans is often identified by palpating the radial or femoral pulse and noting the alternating strength of the beats despite a regular rhythm. It can be confirmed using a blood pressure cuff, where alternating Korotkoff sounds are detected as the cuff pressure is gradually lowered.
• Clinical Implication: The presence of pulsus alternans is a strong indicator of significant left ventricular impairment, and it typically carries a poor prognosis. Its detection should prompt further evaluation and management of potential underlying cardiac dysfunction.

How to Check Pulsus Alternans

To check for pulsus alternans, follow these steps:

Clinical Examination

1. Palpate the Pulse:
   • Use your fingers to palpate the radial or femoral artery.
   • Feel for a regular rhythm but alternating strong and weak pulse amplitudes.
2. Blood Pressure Measurement:
   • Inflate a blood pressure cuff above the systolic pressure.
   • Slowly deflate the cuff while listening to Korotkoff sounds.
   • Alternating loud and soft sounds indicate pulsus alternans.

Advanced Diagnostic Tools

1. Echocardiography:
   • Visualizes heart function and confirms left ventricular dysfunction, which is often associated with pulsus alternans.
2. Electrocardiogram (ECG):
   • May show electrical alternans, which can correlate with pulsus alternans.
3. Cardiac Catheterization:
   • Provides detailed insights into heart function and hemodynamics.

Pulsus Alternans vs Pulsus Paradoxus

Pulsus Alternans vs Pulsus Bigeminus

 Electrical Alternans vs Pulsus Alternans

Treatment for Pulsus Alternans

Pulsus alternans itself is not a disease but a clinical sign indicating severe left ventricular dysfunction, often associated with advanced heart failure. Therefore, its treatment focuses on addressing the underlying cause. Here are the key approaches:

1. Medical Management

• Heart Failure Treatment:
  • Use of diuretics to reduce fluid overload and alleviate symptoms of heart failure.
  • ACE inhibitors or ARBs to improve cardiac function and reduce afterload.
  • Beta-blockers to enhance heart efficiency and control heart rate.
  • Aldosterone antagonists for additional heart failure management.
• Inotropic Agents:
  • Medications like dobutamine or milrinone may be used in acute settings to improve cardiac contractility.

2. Device Therapy

• Implantable Cardioverter-Defibrillators (ICDs):
  • For patients at risk of life-threatening arrhythmias.
• Cardiac Resynchronization Therapy (CRT):
  • Helps improve the coordination of heart contractions in patients with heart failure and conduction abnormalities.

3. Lifestyle Modifications

• Dietary Changes:
  • Low-sodium diet to manage fluid retention.
• Exercise:
  • Supervised cardiac rehabilitation programs to improve overall cardiovascular health.

4. Advanced Interventions

• Surgical Options:
  • In severe cases, procedures like valve repair/replacement or coronary artery bypass grafting (CABG) may be necessary.
• Heart Transplant:
  • Considered for end-stage heart failure when other treatments are ineffective.

5. Monitoring and Follow-Up

• Regular follow-up with a cardiologist to monitor heart function and adjust treatment as needed.

REFERENCES

1. Bickley, L. S., Szilagyi, P. G., Hoffman, R. M., & Soriano, R. P. (2021). Bate’s Guide to Physical Examination and History Taking (13th ed.). Wolters Kluwer Health: Philadelphia.
2. Henery D, Tummala R. Pulsus Alternans. [Updated 2023 Apr 3]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK557642/
3. Burns, S., & Delgado, S. (2019). AACN Essentials of Critical Care Nursing (4th ed.). The McGraw-Hill Companies.
4. Griffin, B., Menon, V., Wiggins, N., Bumgarner, J., & Huded, C. (2019). Manual of cardiovascular medicine (5th ed.). Wolters Kluwer.McLaughlin, M. (2015). Cardiovascular Care Made Incredibly Easy (3rd ed.). Wolters Kluwer.
5. Corlucci, W.S. & Borlaug, B.A. (2021, March 4). Heart failure: Clinical manifestations and diagnosis in adults. UpToDate. https://www.uptodate.com/contents/heart-failure-clinical-manifestations-and-diagnosis-in-adults
6. Gersh, B.J. (2021, November 2). Examination of the arterial pulse. UpToDate. https://www.uptodate.com/contents/examination-of-the-arterial-pulse

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