Key Insights on Heart Transplant Physiology and Complications

Contributor: Travis Barlock, MD

Educational Pearls:

• Key clinical considerations when managing heart transplant patients due to their unique pathophysiology

• 1. Arrhythmias

• A transplanted heart is denervated, meaning it lacks autonomic nervous system innervation

• The lack of vagal tone results in an increased resting heart rate

• Adenosine can be used since it primarily slows conduction through the AV node 

• Atropine is ineffective in treating transplant bradyarrhythmia because its mechanism is to inhibit the vagus nerve - but the heart lacks vagal tone

• Allograft rejection can also cause tachycardia

• Consult transplant surgery - treatment is usually 500 mg methylprednisolone

• 2. Rejection

• Transplant patients are administered immunosuppressants

• Clinical presentation of acute rejection looks similar to heart failure with increased BNP, increased troponin, and pulmonary edema 

• Cardiac allograft vasculopathy is a form of chronic rejection

• Patients will not report chest pain due to denervated heart

• Symptoms are usually weakness and fatigue

• 3. High risk of infection due to immunosuppression

• Increased risk of infections which includes CMV, legionella, tuberculosis, etc

• Immunosuppressants have side effects such as acute kidney injury or pancytopenia

• 4. Radiographic Cardiomegaly

• A study found that radiographic cardiomegaly does not connote heart failure

• They hypothesized it is instead the result of a mismatch between the size of the transplanted heart and the space in the thoracic cavity 

References

1. Murphy JD, Mergo PJ, Taylor HM, Fields R, Mills RM Jr. Significance of radiographic cardiomegaly in orthotopic heart transplant recipients. AJR Am J Roentgenol. 1998 Aug;171(2):371-4. doi: 10.2214/ajr.171.2.9694454. PMID: 9694454.

2. Park MH, Starling RC, Ratliff NB, McCarthy PM, Smedira NS, Pelegrin D, Young JB. Oral steroid pulse without taper for the treatment of asymptomatic moderate cardiac allograft rejection. J Heart Lung Transplant. 1999 Dec;18(12):1224-7. doi: 10.1016/s1053-2498(99)00098-4. PMID: 10612382.

3. Pethig K, Heublein B, Wahlers T, Dannenberg O, Oppelt P, Haverich A. Mycophenolate mofetil for secondary prevention of cardiac allograft vasculopathy: influence on inflammation and progression of intimal hyperplasia. J Heart Lung Transplant. 2004 Jan;23(1):61-6. doi: 10.1016/s1053-2498(03)00097-4. PMID: 14734128.

Summarized by Meg Joyce, MS1 | Edited by Meg Joyce & Jorge Chalit, OMS3

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