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The effect of heart rate control on myocardial ischemia among high-risk patients after vascular surgery
K E Raby1, S J Brull, F Timimi
1Department of Medicine, Boston University School of Medicine, Massachusetts, USA. Khether.Raby@BMC.ORG
Insights
High-risk vascular surgery patients benefit from strict heart rate control. Beta-blocker therapy targeting the individual ischemic threshold significantly reduced postoperative myocardial ischemia, a key marker of cardiac events.
Area of Science:
- Cardiology
- Vascular Surgery
- Anesthesiology
Background:
- Vascular surgery patients face high risks of major postoperative cardiac events.
- Preoperative myocardial ischemia, detected by Holter monitoring, identifies a high-risk subgroup.
- Postoperative ischemia in this subgroup often precedes major cardiac events.
Purpose of the Study:
- To determine if patient-specific postoperative heart rate control with beta-adrenergic blockers reduces postoperative ischemia in high-risk vascular surgery patients.
- To investigate the efficacy of targeting heart rate below the individual ischemic threshold.
Main Methods:
- 150 patients undergoing elective vascular surgery were monitored preoperatively by 24-h Holter.
- 26 patients with significant myocardial ischemia (ST-segment depression) were identified.
- These patients were randomized to receive intravenous esmolol or placebo, aiming for heart rate 20% below their ischemic threshold for 48 hours postoperatively.
Main Results:
- Postoperative ischemia persisted in 73% of placebo patients versus 33% of esmolol patients (P < 0.05).
- Among esmolol patients, 9/9 with heart rates below the ischemic threshold showed no postoperative ischemia.
- Two cardiac events occurred in patients with postoperative ischemia and heart rates exceeding the threshold.
Conclusions:
- Patient-specific heart rate control targeting a predefined ischemic threshold significantly reduces postoperative myocardial ischemia in high-risk vascular surgery patients.
- This strategy may eliminate postoperative ischemia and warrants further investigation in larger trials to assess its impact on cardiac risk.
Unlabelled:
Patients undergoing vascular surgery have a high risk of suffering major postoperative cardiac events. Preoperative myocardial ischemia as detected by Holter monitoring identifies a high-risk subgroup whose postoperative ischemia, similarly detected, seems to herald major cardiac events. In this study, we determined whether systematic, patient-specific postoperative heart rate control with beta-adrenergic blocker therapy decreases the incidence of postoperative ischemia among high-risk vascular surgery patients. A total of 26 of 150 patients who underwent elective vascular surgery and were monitored preoperatively by 24-h Holter were found to have significant myocardial ischemia as defined by ST-segment depression. The minimal heart rate at which this ST-segment depression occurred was identified (ischemic threshold), and these 26 patients were then randomized to receive continuous i.v. beta-blockade with esmolol or placebo plus usual medical therapy, aiming to reduce the postoperative heart rate to 20% below the ischemic threshold. All patients were monitored by Holter for 48 h postoperatively. Postoperative Holter readings were analyzed for the incidence of ischemia and for the number of hours during which heart rate was controlled below the ischemia threshold. Patients had a median of two episodes of preoperative ischemia lasting a median of 30 min (range 1-155 min). A total of 15 patients were randomized to receive esmolol, and 11 were randomized to receive placebo. The two groups were comparable with respect to clinical characteristics and incidence and duration of preoperative ischemia. Ischemia persisted in the postoperative period in 8 of 11 placebo patients (73%), but only 5 of 15 esmolol patients (33%) (P < 0.05). Of the 15 esmolol patients, 9 had mean heart rates below the ischemic threshold, and all 9 had no postoperative ischemia. A total of 4 of 11 placebo patients had mean heart rates below the ischemic threshold, and 3 of the 4 had no postoperative ischemia. There were two postoperative cardiac events among patients who had postoperative ischemia (one placebo, one esmolol) and whose mean heart rates exceeded the ischemic threshold. Our data suggest that patient-specific, strict heart rate control aiming for a predefined target based on individual preoperative ischemic threshold was associated with a significant reduction and frequent elimination of postoperative myocardial ischemia among high-risk patients and provide a rationale for a larger trial to examine this strategy's effect on cardiac risk.
Implications:
Patients who undergo peripheral vascular surgery often experience transient cardiac complications and/or permanent heart damage just after surgery because of inadequate myocardial blood flow. In this study, we identified patients at high risk of cardiac complications after vascular surgery and showed that if their heart rate was carefully controlled for 48 h after surgery, myocardial ischemia, a common marker of heart injury, was markedly reduced.