Assessing Coronary Vasomotor Function in a Patient With SIHD With Unobstructed Coronary Arteries
A 65-year-old woman with medical history of smoking, myocardial infarction, hypertension, chronic obstructive pulmonary disease, and migraine is evaluated in the clinic for anginal chest pain. The patient reports episodic chest pain that is retrosternal and radiates to the jaw for the last 4 months. The pain is mostly exertional but sometime occurs without clear triggers. Each episode usually lasts up to 20 minutes before spontaneous resolution. She had an anterior ST-segment elevation myocardial infarction 2 years before, and the coronary angiogram then showed subtotal occlusion of the mid left anterior descending artery (LAD), which was revascularized with a drug-eluting stent. A subsequent echocardiogram showed normal left ventricular ejection fraction with no wall motion abnormalities. Her current medications include aspirin 81 mg daily, carvedilol 6.25 mg twice daily, lisinopril 10 mg daily, isosorbide mononitrate 30 mg daily, and rosuvastatin 20 mg daily.
On examination, her body mass index is 31 kg/m2, heart rate is 72 bpm, and blood pressure is 135/85 mmHg. Cardiovascular examination discloses normal first and second heart sounds with no rubs, gallops, or murmurs. The rest of examination is unremarkable. An electrocardiogram (ECG) in the office shows normal sinus rhythm and no ST-T wave abnormalities. An ECG done during an emergency department visit for chest pain showed a normal sinus rhythm with T-wave inversions in leads V4-V6. The patient was then referred for invasive coronary angiogram, which showed a patent stent in the mid LAD with no evidence of obstructive coronary artery disease (CAD) in the other coronary arteries. Given the nature of her symptoms, as well as risk factors, provocation testing with intracoronary acetylcholine was done, during which the patient experienced similar anginal chest pain but without any significant epicardial coronary spasm on angiography.
Which, if any, of the following tests is most likely to be abnormal in this patient and provide additional prognostic information?