Heart Block Itself Does Not Worsen Prognosis After AMI

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Although patients with heart block during acute myocardial infarction (AMI) have poorer 30-day outcomes, the difference can be explained by worse baseline characteristics compared with those without the complication, reports a Korean registry study published online September 16, 2014, ahead of print in the American Journal of Cardiology.

Methods
Sang-Hyun Kim, MD, of Seon National University Boramae Medical Center (Seoul, South Korea), and colleagues analyzed data from 2 South Korean registries on 13,862 patients who had AMI between January 2005 and June 2013. Among them, 89.8% received DES.

Second-degree (Mobitz type I or II) or third-degree atrioventricular block (AVB) occurred in 378 patients (2.7%). Such patients were more likely to be older and women and to have more unfavorable clinical characteristics, including Killip class ≥ 2, diabetes, hypertension, lower blood pressure, high glucose levels, and poorer renal function compared with those without heart block. Patients with AVB were also less likely to be discharged on a beta-blocker.

At 30 days, the rate of MACE (all-cause death, recurrent MI, and repeat revascularization) was 8.2% overall and higher for patients who did vs did not have AVB (table 1).

Table 1. Clinical Outcomes at 30 Days After AMI

 

Heart Block

(n = 378)

 

No Heart Block

(n = 13,484)

 

P Value

MACE

16.7%

8.0%

< .001

Cardiac Death

13.8%

5.5%

< .001

Nonfatal MI

0.3%

0.5%

< .001

Repeat Revascularization

    PCI

    CABG

 

1.3%

0

 

0.9%

0.3%

 

.463

.630

 

On multivariate analysis, however, heart block did not predict 30-day MACE risk (OR 0.71; 95% CI 0.28-1.78). Independent predictors of greater risk were:

 

  • Male sex: OR 1.62; 95% CI 1.12-2.33
  • Hypertension: OR 1.45; 95% CI 1.05-1.98
  • Killip class ≥ 2: OR 1.67; 95% CI 1.20-2.31
  • Triple-vessel CAD: OR 1.48; 95% CI 1.06-2.05
  • LVEF ≤ 40%: OR 1.54; 95% CI 1.13-2.10
  • Estimated GFR < 60 mL/min/1.73 m2: OR 1.85; 95% CI 1.28-2.68

 

The culprit artery was the RCA in most patients with heart block (83.8%) and most commonly the LAD in patients without the complication (48.4%). Among patients with heart block, the rate of MACE was higher for the minority whose culprit artery was the LAD compared with the RCA or LCX, a difference mainly due to cardiac death. Multiple logistic regression analysis confirmed that having a culprit lesion in the LAD carried an added risk of 30-day MACE (OR 5.28; 95% CI 1.22-22.81) in patients with AVB.

Findings Stem From Shift in Practice

The incidence of AVB was several percentage points lower in the current study than in earlier reports, Dr. Kim and colleagues report, attributing the improvement to more rapid reperfusion using more advanced techniques and effective medications in the DES era.

The decline in heart block could potentially “reflect parallel reductions in the severity of myocardial injury,” they hypothesize, adding that AVB appears to “be a surrogate marker of severity and extension of infarction.”

 


Source:
Kim H-L, Kim S-H, Seo J-B, et al. Influence of second- and third-degree heart block on 30-day outcome following acute myocardial infarction in the drug-eluting stent era. Am J Cardiol. 2014;Epub ahead of print.

 

Disclosures:

 

  • The paper contains no statement on potential conflicts of interest for Dr. Kim.

 

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