Case Presentation:

A 63–year–old man presented with ten days of dyspnea on exertion, occurring with minimal exertion and resolving after rest. He reported associated palpitations, fevers, chills, and increasing abdominal girth, but denied chest pain, orthopnea, paroxysmal nocturnal dyspnea, lightheadedness, nausea, vomiting, or diaphoresis. He had a history of untreated hepatocellular carcinoma (HCC). His temperature was 100.3°F, his heart rate ranged from 120 to 135 bt/min, and his blood pressure was 136/82 mmHg. He was noted to be tachypneic after taking only a few steps in the examination room, though his cardiac and pulmonary exams were normal. He had a moderately distended abdomen with shifting dullness near the flanks; there was no lower extremity edema. An EKG depicted an abnormal P wave axis and first–degree atrio–ventricular block, suggesting ectopic atrial tachycardia. P waves were obscured by the preceding T waves, and demonstrated a return to an isoelectric baseline. The initial troponin I was 0.95. Urine toxicology was negative. The serum electrolytes and CBC were normal. Computed tomography of the chest with intravenous contrast revealed a neoplastic process of the right lobe of the liver and associated tumor thrombus extending through the inferior vena cava and into the right atrium. The patient left the hospital against medical advice before undergoing any additional investigation or treatment.

Discussion:

Tachy–arrhythmias are commonly encountered by the hospitalist. Though sinus tachycardia is the most common, the hospitalist must be adept at recognizing atrial tachycardia, and when present, formulating a differential diagnosis for its cause. The hallmark of atrial tachycardia is the shortened PR interval, and a change in the P wave axis, as the source of the ectopic pacemaker is located elsewhere within the atria. The overwhelming majority of patients with atrial tachycardia will have chronic obstructive lung disease, with subsequent stretching of the right atria, as the cause. In patients without this history, however, the hospitalist must know to look for alternative causes of atrial irritation or hyper–excitablity. The most common of these causes include digoxin, thyrotoxicosis, amphetamines or cocaine, central line catheters or tumor invasion.

Conclusions:

A variety of sub–diaphragmatic tumors, including hepatocellular carcinoma (HCC), are known to spread by extension through the inferior vena cava. In this case, the HCC invaded the right atrium via the inferior vena cava. Although cardiac metastases are rare, direct extension through the vena cava is commonly observed when cardiac involvement occurs. Proposed arrhythmogenic mechanisms include neoplastic invasion of an atrial sympathetic nerve, invasion of tumor thrombus into atrial arteries, and direct tumor extension into the myocardium with subsequent stimulation of an ectopic pacemaker.