The Heart Point Sign: Description of a New Ultrasound Finding Suggesting Pneumothorax

A 58-year-old man with recently diagnosed diabetes mellitus presented to the emergency department after a syncopal event with a prodrome of lightheadedness. According to witnesses, he woke up quickly and complained of left-sided chest pain immediately after the fall. He had no chest pain prior to the event and denied shortness of breath, diaphoresis, palpitations, or dizziness at the time of evaluation. He was in no respiratory distress and was alert and oriented to person, place, and time. His vital signs were temperature 97.8°F, heart rate 115 beats/min, respiratory rate 18 breaths/min, blood pressure 90/61 mm Hg, and oxygen saturation 99% while breathing room air. His physical exam was otherwise unremarkable.

While awaiting portable chest radiography, a bedside cardiac ultrasound (US) was performed by the emergency physician using a 5–1 MHz phased array transducer (SonoSite MTurbo, Bothell, WA). Although the subcostal view was unremarkable, upon imaging the parasternal region, the provider noted a flickering phenomenon where the heart was clearly visualized in late diastole, but would disappear in midsystole only to reappear in late diastole during the next cardiac cycle (Video Clip S1). Given the beat-to-beat variability in the visualization of the heart, the provider suspected that air was being transiently interposed between the chest wall and the heart during the cardiac cycle.

At this point the physician performed a lung US with both a 5–2 MHz curved array probe and a 10–5 MHz linear probe to determine if a pneumothorax was present. This revealed absent lung sliding on the left and normal lung sliding on the right. The physician confirmed the diagnosis of pneumothorax by locating a “lung point” in the left midaxillary line at the 10th interspace (Video Clip S2). Due to the proximity of the diaphragm in this caudad location, an unusual pattern of intermittent lung sliding (on the left side of the screen) and diaphragmatic motion (on the right side) was observed.

Chest radiography was obtained 20 minutes after the US examination and confirmed a moderate left-sided pneumothorax (Figure 1). The patient remained clinically stable and a noncontrast chest computed tomography (CT) was performed 2 hours later, which revealed a moderately large left pneumothorax without evidence of tension or mediastinal shift, nondisplaced fractures of the left posterior 9th and 10th ribs, and mild subsegmental atelectasis at the left lung base (Figure 2). The CT demonstrates the extension of the pneumothorax over the anterior mediastinum and heart.

Figure 1.  Anteroposterior chest radiography demonstrating a left pneumothorax.

Figure 2.  Representative image from noncontrast CT scan of the thorax demonstrates a moderate sized pneumothorax with air interposed between the anterior chest wall and the heart. CT = computed tomography.

The patient had a left thoracostomy tube placed and a repeat chest x-ray demonstrated reexpansion of the lung. The patient’s syncope was attributed to recently starting 25 mg of enalapril, and his dose was decreased to 10 mg while he was hospitalized. The thoracostomy tube was removed on hospital day 5, and the patient was discharged home uneventfully.

This report highlights the identification of a new sign, the “heart point” sign, a previously undescribed phenomenon specific to pneumothorax. As the heart fills with blood in diastole, it enlarges and displaces the air from the precardiac space, allowing the heart to transiently contact the chest wall and be visualized with US. As the heart contracts during systole, the pneumothorax fills the space between the heart and the anterior chest wall, preventing the transmission of US and causing the heart to momentarily disappear from view. Providers should be aware of this phenomenon as, in this case, it may be the first clue to the presence of an unsuspected pneumothorax.