Paradoxical Sinus Bradycardia in the Setting of Acute Cardiac Tamponade: A Case Report

Cardiac tamponade is a life-threatening condition classically associated with compensatory sinus tachycardia due to impaired diastolic filling and reduced cardiac output; however, paradoxical sinus bradycardia is rare and may delay recognition. We report a case of a 43-year-old woman with obesity status post gastric sleeve, asthma, and hyperlipidemia who presented with two weeks of progressive dyspnea, pleuritic chest pain, and chest tightness following a suspected viral syndrome, with symptoms worsening supine and improving when leaning forward. Initial evaluation demonstrated muffled heart sounds, sinus rhythm with electrical alternans on electrocardiography, cardiomegaly on chest radiography, and a large pericardial effusion on point-of-care ultrasound without initial tamponade physiology. While awaiting further workup, she developed recurrent syncope with profound sinus bradycardia and transient pulselessness requiring vasopressor support. Transthoracic echocardiography revealed right atrial compression and right ventricular diastolic collapse consistent with acute cardiac tamponade. Urgent pericardiocentesis drained 1.3 liters of bloody, turbid fluid with immediate resolution of bradycardia and hemodynamic instability. Pericardial fluid analysis was exudative with inflammatory cells, and there was no evidence of malignancy. The patient was successfully treated with high-dose aspirin and colchicine without recurrence. Notably, the absence of compensatory tachycardia in this case contributed to delayed clinical recognition of tamponade physiology. This case highlights that cardiac tamponade may rarely present with paradoxical sinus bradycardia rather than tachycardia, underscoring the importance of maintaining clinical suspicion and performing prompt echocardiographic assessment, as urgent pericardial drainage can be life-saving even in nonclassical presentations.