MON-760 - Acute Heart Failure Revealing Pseudohypoparathyroidism: A Case of Hypocalcemic Cardiomyopathy

Background: Hypocalcemic cardiomyopathy is a rare but highly reversible cause of acute heart failure. Pseudohypoparathyroidism (PHP), characterized by PTH resistance, represents an uncommon etiology with an estimated prevalence of 0.79 per 100,000. Extracellular calcium plays a critical role in myocardial excitation-contraction coupling through the actin-myosin interaction via the troponin-tropomyosin complex [1]. Chronic hypocalcemia reduces calcium entry through L-type channels, diminishing intracellular calcium available to bind troponin C and hindering cross-bridge formation, ultimately weakening myocardial contractility [1].

Clinical

Case: A 58-year-old male presented with a one-week history of progressive dyspnea on exertion, orthopnea, and paroxysmal nocturnal dyspnea. He was initially tachycardic to 115, tachypneic to 28. Laboratory findings revealed profound hypocalcemia (4.7 mg/dL, normal 8.5-10.5 mg/dL), hyperphosphatemia (7.7 mg/dL, normal 2.5-4.5 mg/dL), elevated PTH (171.5 pg/mL, normal 10-65 pg/mL), and elevated BNP (654 pg/mL, normal < 100). Transthoracic echocardiogram demonstrated a severely dilated left ventricle, dilated left atrium, moderate-to-severe mitral regurgitation with LVEF 35-40%. Given normal eGFR (55, repeat >60 next day), secondary hyperparathyroidism from CKD was excluded. Absence of skeletal abnormalities established a diagnosis of PHP-1b. Cardiac catheterization revealed global hypokinesis without ischemia. Autoimmune, inflammatory, toxic, medication-induced, and infectious etiologies were excluded. Hypocalcemia was treated with calcitriol, calcium supplements, phosphate binders, and guideline-directed medical therapy was initiated for heart failure. After 5 days, dyspnea was completely resolved, along with normalization of serum calcium levels.

Conclusion: This case demonstrates a rare but serious complication of inadequately treated PHP— dilated cardiomyopathy. Hypocalcemic cardiomyopathy is highly responsive to calcium and vitamin D supplementation, with up to 94% of patients demonstrating recovery from myocardial dysfunction [1]. This case emphasizes the importance of checking serum calcium in patients with new-onset cardiomyopathy of unclear etiology and highlights the cardiac manifestations of chronic hypocalcemia.

Reference: (1) Sliwa K, Viljoen CA, Hasan B, Ntusi NAB. Nutritional Heart Disease And Cardiomyopathies: JACC Focus Seminar 4/4. J Am Coll Cardiol. 2022;81(22):2132-2151.

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