Acute myocardial infarction in patients with hypertension: Association with adverse prognostic indicators

An impaired baroreceptor reflex sensitivity controlling the heart period through the vagus nerves (BRS) and sympatho-humoral activation following acute myocardial infarction (AMI) represent adverse prognostic indices. The occurrence of AMI in patients with hypertension (HT-AMI) is not unexpected, and has been associated with a greater mortality than that occurring in normotensive subjects (NT-AMI). This study was planned to determine whether HT-AMI patients have a greater central sympathetic output and BRS impairment than NT-AMI patients. We examined 11 HT-AMI, 10 NT-AMI patients 2-4 days following AMI and 10 normal control (NC). The groups were matched according to age, body mass index (BMI) and gender (Table). The two AMI groups were also matched according to heart rate (HR). Muscle sympathetic nerve activity (MSNA) was measured by microneurography from the peroneal nerve and quantified in terms of bursts per 100 cardiac beats (b/100b). BRS was obtained from the Valsalva maneuver as the steepest slope between the RR interval (ms) and systolic pressure (mmHg). Data were expressed as mean SEM and summarised in the table below. Mean arterial pressure (MBP) was insignificantly lower in NT-AMI and the HR was higher in NC than NT-AMI (P 0.05; ANOVA posttests). MSNA hyperactivity relative to NC was greater in HT-AMI than in NT-AMI (at least P 0.05) whilst BRS impairment (at least P 0.01) was insignificantly greater in HT-AMI than NT-AMI. These results in patients following AMI indicate that pre-existent hypertension leads to an excessive level of sympathetic activation and BRS impairment, and may at least partly explain the adverse prognosis seen in hypertensive patients following AMI.