Review Question - QID 217308

This man presenting with hypotension, distended neck veins, diminished heart sounds, pulsus paradoxus (decrease in systolic blood pressure by >=10 mmHg with inspiration), and ECG findings of electrical alternans and decreased voltages following multiple missed dialysis appointments has likely developed cardiac tamponade due to uncontrolled uremia and requires immediate pericardiocentesis to drain the excess fluid from the pericardial sac.

Cardiac tamponade is a life-threatening condition that occurs due to an accumulation of fluid within the pericardial sac resulting in increased pericardial pressure, decreased left ventricular filling, and subsequent decreased cardiac output and fulminant obstructive shock. Major etiologies of cardiac tamponade include penetrating trauma, malignancy, uremia, infectious, post-cardiotomy, and post-acute myocardial infarction. Exam findings include Beck triad (hypotension, jugular venous distention, and muffled heart sounds) as well as pulsus paradoxus (inspiratory decline in systolic blood pressure > 10 mmHg). Diagnosis is often made with an bedside echocardiogram demonstrating increased pericardial fluid with right ventricular collapse. Other supportive findings include electrical alternans and low voltages on ECG and an enlarged cardiac silhouette on chest radiograph. Treatment of cardiac tamponade is emergent pericardiocentesis typically followed by a pericardial window for long-term control.

Spodick reviews the clinical presentation and management considerations for patients with acute cardiac tamponade. The author highlights 2 key aspects of the management of acute cardiac tamponade. First, mechanical ventilation with positive airway pressure can further decrease cardiac output and should not be utilized. Second, cardiopulmonary resuscitation for patients with cardiac tamponade and cardiac arrest has a negligible impact due to the failure of external compressions to address the underlying issue of ventricular filling.

Figure/Illustration A is an ECG demonstrating electrical alternans which refers to the alternation of QRS voltage magnitudes due to the heart swinging within the fluid-filled pericardial sac as can be seen best on the rhythm strip in lead II (red arrows). Additional findings suggestive of cardiac tamponade include sinus tachycardia and decreased QRS voltages.

Incorrect Answers:
Answer 1: Cardiac catheterization is indicated in patients within 12 hours of an ST-elevation myocardial infarction (STEMI) which is identified on ECG with ST elevations corresponding to a coronary artery territory.

Answer 2: Low-molecular-weight heparin is the treatment for a pulmonary embolism that presents with dyspnea, pleuritic chest pain, hemoptysis, and hemodynamic instability.

Answer 3: Needle decompression of the pleural space is the treatment for a tension pneumothorax which can also present with obstructive shock. However, unlike in this patient who has clear breath sounds bilaterally, a tension pneumothorax leads to a collapsed lung resulting in unilaterally absent breath sounds and tracheal deviation away from the affected side.

Answer 5: Synchronized cardioversion is often reserved for hemodynamically unstable patients with the following arrhythmias: ventricular tachycardia, supraventricular tachycardia, atrial fibrillation, and atrial flutter. Although this patient demonstrates signs of hemodynamic instability such as hypotension and tachycardia, the ECG shows electrical alternans rather than any of the arrhythmias amenable to synchronized cardioversion.

Bullet Summary:
Patients with cardiac tamponade present with jugular venous distention, hypotension, muffled heart sounds, and electrical alternans on ECG and require emergent pericardiocentesis.