A common cause of exertional dyspnea is an inducible laryngeal obstruction (ILO), where the vocal folds adduct inappropriately during respiration. However, exertional dyspnea can also be caused by cardiac, hematologic, metabolic, neurologic, pulmonary, and tracheobronchial disorders.
This broad differential diagnosis requires vigilance and a low threshold for multidisciplinary evaluation. ILO can be a challenging diagnosis because of nonspecific symptoms, co-occurrence with asthma and other disorders, and a dynamic course that can elude capture on laryngeal examination.
Physicians at Brigham and Women’s Hospital recently encountered a patient with exertional dyspnea and ILO at rest who was ultimately diagnosed with hypertrophic cardiomyopathy as the cause of his symptoms. Thomas L. Carroll, MD, director of the Voice Program and section chief of Laryngology, Bradley M. Wertheim, MD, a member of the Pulmonary Vascular Disease Program, and colleagues describe the case in the Journal of Voice. They encourage wider use of cardiopulmonary exercise testing (CPET) with intermittent or continuous laryngeal examination (ILE or CLE) to catch high-risk cardiopulmonary mimics of upper airway symptoms.
Description of the Case
The patient, a 55-year-old man, presented with progressive exertional throat tightness and dyspnea. He was a competitive long-distance runner and previously ran over 50 miles per week at a 7-minute mile pace. Still, he had developed increasing dyspnea with hill running approximately eight years previously.
Four years before presentation, the patient had been diagnosed with exercise-induced asthma but did not respond to anti-asthma medication. Several months before presentation, he developed worsening exertional symptoms, including heavy breathing, “gasping,” a sensation of being unable to inhale, and discomfort at the base of his throat beginning approximately 2 minutes after starting to run and ending after cessation of exercise.
He also endorsed frequent burping, vocal fatigue, and nocturnal episodes of self-described airway obstruction at the level of the larynx in the supine position. These symptoms persisted after a trial of asthma therapy and omeprazole.
On flexible laryngovideostroboscopy, his vocal folds were observed to be adducting during exhalation on quiet respiration. He also demonstrated compensatory laryngeal hyperfunction and nonspecific laryngeal edema. A voice pathologist provided respiratory retraining and the patient received an empiric trial of acid suppression therapy.
Lung function tests were normal except the forced expiratory volume in 1 second/forced vital capacity ratio was 68%, consistent with a borderline obstructive defect. Still, that would not be expected to cause substantial exercise limitations.
Because the patient’s symptoms seemed disproportionate to the findings, he underwent CPET with ILE. He developed atrial flutter with 1:1 atrioventricular conduction to a heart rate of 244 beats/min, coinciding with the onset of dyspnea and throat tightness. The test also showed impaired aerobic capacity and ventilatory inefficiency. Aerobic capacity is typically normal in the setting of ILO.
After referral, a cardiology evaluation revealed an abnormal transthoracic echocardiogram and cardiac MRI study consistent with apical-variant hypertrophic cardiomyopathy. He underwent cavotricuspid isthmus ablation with subsequent improvement in exercise capacity. An implantable cardioverter–defibrillator was placed for the prevention of sudden cardiac death.
Guidance for the Clinic
Many otolaryngologists have their dyspneic ILO-suspect patients undergo outpatient, in-office exercise challenges, such as the stair-climbing challenge. This option is rapid and inexpensive, however, it could be dangerous if a patient became symptomatic from non-ILO causes and it can miss potentially important causes of dyspnea, as this case demonstrates.
CPET with intermittent or continuous laryngeal evaluation should be considered when: (a) resting fiberoptic laryngoscopy is abnormal but symptoms do not improve with therapy, or (b) resting laryngoscopy is normal and pulmonary, cardiac, and general medical evaluations are also unrevealing.