Abstract 1409: Coronary Artery Disease Patients Have Markedly Impaired Arterial Baroreflexes Even in Absence of Cardiac Dysfunction
BACKGROUND. It is well documented that those coronary artery disease (CAD) patients whose arterial baroreflex (ABR) function is impaired are exposed to an increased risk of arrhythmic death. It is however surprisingly ill-documented whether baroreflex impairment is a feature of the CAD patient population at large. It is also unclear whether having suffered a myocardial infarction (MI) affects BR function, and whether in these patients the BR impairment is confined to the cardiac or extends to the vascular component of the reflex.
METHODS: Twenty patients with significant CAD, aged 64±1 yrs, all candidates to coronary surgery, 8 with previous MI, 13 with hypertension, none with left ventricular (LV) dysfunction (all with ejection fraction >50%), were subjected to graded neck suction (−20 and −40 mmHg for 60 sec) to examine the reflex bradycardic (increases in R-R interval, RRI, EKG) and vasodepressor (reductions in blood pressure, BP, Finapres) responses to carotid baroreceptor stimulation. Concurrent groups of age-matched normal controls (NCtrl, n=9) and LV dysfunction patients (n=25, all with ejection fraction <35%) were identically studied. Baroreflex sensitivity was expressed as the slope of the regression of RRI and BP responses to stimulus intensity.
RESULTS: Baroreflex control of RRI was significantly reduced in CAD patients compared to NCtrl: 1.42±0.2 vs 2.17±0.4 msec.mmHg (means±SEM, −35%, p<0.03); the same applied to BR control of BP: −0.13±0.02 vs −0.24±0.05 mmHg.mmHg-1 (−46%, p<0.002). The baroreflex impairment of CAD patients was of similar magnitude as that of LV dysfunction patients (BR-RRI 1.37±0.1 msec.mmHg-1, BR-BP −0.09±0.01 mmHg.mmHg-1, both p=ns vs CAD patients). There was also no significant difference, within CAD patients, in BR-RRI or BR-BP between individuals with and without a previous MI (data not shown).
CONCLUSIONS: Baroreflex impairment
is a characteristic of the CAD patient, even in absence of LV dysfunction;
is observed irrespective of the previous occurrence of an MI;
is no less pronounced in CAD than in LV dysfunction patients;
affects not only the bradycardic but also the vasodepressor component of the baroreflex, a feature that differentiates it from the BR impairment observed in hypertension.