Abnormal Left Ventricular Contractile Response to Exercise Without Obstructive Coronary Disease: A Newly Described Phenomenon Associated with Subclinical Myocardial Dysfunction

Abstract

Background: Failure of left ventricular (LV) contractile reserve or reduced ejection fraction (EF) post-exercise is an abnormal stress echocardiography (ESE) response. The aetiology in the absence of obstructive coronary artery disease (CAD) or hypertensive response is unclear, but possibly related to either microvascular dysfunction or subclinical myocardial dysfunction. Methods: Of 5,275 consecutive patients undergoing ESE for suspected CAD between 2009 and 2012, 1,134 had angiography within 90 days. Excluding those with obstructive CAD, hypertensive response, failure to achieve target heart rate, resting LVEF < 50% or valvular disease, we identified 110 patients with abnormal LV contractile response (abnormal ESE) and 212 with normal response (normal ESE). Resting echocardiogram mitral annular velocities (e′) were measured to assess subclinical myocardial function. Myocardial blush grade (MBG) and corrected TIMI frame count (CTFC) were determined angiographically to assess microvascular function. Results: Comparing normal ESE vs. abnormal ESE, there was no difference in age (60 ± 11 vs. 61 ± 10), BMI (29.1 ± 5.4 vs. 29.5 ± 6.4), hypertension (53% vs. 55%) or diabetes (16% vs. 20%), but a higher proportion of females with abnormal ESE (82% vs. 53%, p < 0.001). Resting LVEF was similar (60 ± 6% vs. 62 ± 6%, p = 0.05); post-exercise LVEF was lower in abnormal ESE (54 ± 8% vs. 75 ± 6%, p < 0.001). Abnormal ESE had higher LV mass-index (80 ± 21 vs. 73 ± 19 g/m2, p = 0.006), lower septal (6.1 ± 1.9 vs. 7.7 ± 2.2 cm/s) and lateral (8.1 ± 2.9 vs. 10.4 ± 3.0) e′ velocities (p < 0.001), larger left atrial volume index (37.3 ± 10.1 vs. 31.1 ± 7.2 ml/m2, p < 0.001), and lower exercise capacity (8.8 ± 3.0 METS vs. 10.5 ± 4.3 METS, p < 0.001). There was no difference in MBG or CTFC. Conclusions: An abnormal LV contractile response to exercise in the absence of obstructive CAD is most frequently seen in middle-aged females and is associated with subclinical LV myocardial dysfunction, but not with microvascular dysfunction.