Hemodynamically Significant Extrinsic Left Atrial Compression by Gastric Structures in the Mediastinum

Case Reports

Patient 1

A 60-year-old man with squamous cell carcinoma of the hypopharynx had elective transhiatal esophagectomy, which was complicated by a non-Q wave myocardial infarction. Echocardiography showed inferoapical hypokinesis with normal chamber dimensions. The patient's condition stabilized, and nasogastric suction was discontinued on the fourth day after surgery. One day later, however, the patient became dyspneic and diaphoretic. His systolic blood pressure was 85 mm Hg by palpation, his heart rate was 110 beats/min, and his respiratory rate was 36 breaths/min. Chest examination revealed rales over the lower half of both lung fields. An arterial blood gas test showed hypoxemia and an arterial-alveolar gradient of 43 mm Hg. Echocardiography showed extrinsic left atrial compression (Figure 1, top) with improvement in wall motion. Intravenous fluid resuscitation failed to improve hemodynamic variables, but the removal of 200 mL of bilious fluid from the stomach resulted in immediate improvement in blood pressure to 135/95 mm Hg and improvement in oxygenation. Repeated echocardiography showed a normal left atrium (Figure 1, bottom).

Patient 2

A 94-year-old woman with a previously asymptomatic hiatal hernia developed respiratory distress 2 days after elective inguinal herniorrhaphy. On physical examination, the patient was diaphoretic and in obvious distress. Her blood pressure was 90/60 mm Hg, her pulse rate was 120 beats/min, and her respiratory rate was 30 breaths/min. Her jugular venous pressure was 12 mm Hg. Chest examination revealed rales bilaterally over the lower two thirds of both lung fields. A chest roentgenogram showed bilateral interstitial infiltrates and a new right lower lobe density. An arterial blood gas test showed severe hypoxemia and an arterial-alveolar gradient of more than 30 mm Hg.

The patient was intubated and resuscitated with intravenous fluids and dobutamine. Transthoracic echocardiography showed almost complete obliteration of the left atrium by an extrinsic mass (Figure 2, top). After 800 mL of fluid was removed from the stomach, the patient's blood pressure improved immediately to 125/80 mm Hg, her heart rate declined to 90 beats/min, and dobutamine therapy was discontinued. The patient was subsequently extubated without difficulty. Repeated chest radiography showed a smaller right lower lobe mass with a nasogastric tube coiled within it. Repeated transthoracic echocardiography showed reexpansion of the left atrium (Figure 2, bottom).

Patient 3

An 86-year-old woman had elective pacemaker placement. Placement was complicated by right ventricular perforation, which was successfully treated by insertion of a pericardial catheter without tamponade. On the third day after surgery, however, the patient had acute left-sided chest pain. Her blood pressure was 90/64 mm Hg; her heart rate was 120 beats/min. Transthoracic echocardiography showed a slit-like left atrium compressed by a posterior dense mass. There was no significant residual pericardial effusion. A chest roentgenogram confirmed the presence of a large hiatal hernia; the entire stomach was seen in the posterior mediastinum and gastric volvulus was present. After 950 mL of gastric contents was removed from the stomach, the patient's blood pressure improved immediately to 165/90 mm Hg, her heart rate declined to 90 beats/min, and her pulmonary capillary wedge pressure declined from 28 mm Hg to 12 mm Hg. Repeated echocardiography after endoscopically guided evacuation of the hernial sac showed a normal left atrium.

Discussion

These three cases show hemodynamically significant left atrial compression caused by the displacement of the stomach into the mediastinum; they also show immediate relief of hypotension and amelioration of pulmonary venous congestion after the removal of gastric contents. The left atrium is susceptible to compression from any abnormal adjacent structure, including a dilated stomach or esophagus. Possible mechanisms for the observed decreased cardiac output and pulmonary congestion include obstruction of left atrial inflow and direct impairment of ventricular filling, causing functional tamponade.

D'Cruz and colleagues [1] divide the relation between mediastinal masses and the heart into three categories: proximity (a contiguous or adjacent structure without chamber deformation), encroachment (distortion of normal cardiovascular architecture without hemodynamic effect), and compression. Clinical manifestations of compression include tachycardia, tachypnea, hypotension, and hypoxia, as shown in our patients. Patients may also present with tamponade [6, 7] or shock [8]. The clinical presentation may mimic that seen with more common clinical catastrophes, such as pulmonary embolus, acute myocardial infarction, or acute respiratory failure. We have found only one previous report [9] of a patient who had left atrial encroachment by hiatal hernia that resulted in syncope and in which relief of symptoms was seen after hernia repair [9]. The transient loss of normal gastric motility as a result of abdominal surgery, as in two of our patients, may in part explain our unique findings.

Transthoracic echocardiography is the test of choice for diagnosing left atrial compression. In contrast to intrinsic atrial abnormalities, such as thrombus or myxoma, extrinsic masses move asynchronously with the atria. The stomach can be identified by the echocardiographic appearance of air contrast during the ingestion of liquid containing carbon dioxide [1]. Transesophageal echocardiography may also be useful for the identification of masses adjacent to the left atrium [10, 11].

Left atrial compression by the esophagus, the stomach, or both is an uncommon but important cause of hemodynamic compromise. Timely diagnosis and the prompt removal of gastric contents will usually lead to the return of normal hemodynamic function.