ISCHEMIA
International Study of Comparative Health Effectiveness with Medical and Invasive Approaches
Clinical Question
Population
Patients with stable ischemic heart disease and moderate or severe ischemia on stress testing, excluding those with left main disease (identified by coronary CTA), recent ACS, heart failure (EF <35%), or unacceptable angina on medical therapy.
Initial invasive strategy: cardiac catheterization with revascularization (PCI or CABG) as indicated, plus optimal medical therapy
Initial conservative strategy: optimal medical therapy alone, with catheterization reserved for medical therapy failure
Primary Endpoint
Composite of cardiovascular death, myocardial infarction, hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest
Key Findings
At a median follow-up of 3.2 years, the primary endpoint occurred in 13.3% of invasive vs 15.5% of conservative patients (adjusted HR 0.93; 95% CI, 0.80-1.08; p=0.34).
There was no difference in cardiovascular death (HR 0.92) or all-cause death (HR 1.05) between strategies.
The invasive group had higher rates of periprocedural MI early on, but lower rates of spontaneous MI over time, yielding no net benefit.
Quality of life was significantly better in the invasive group, particularly among patients with frequent angina at baseline.
The conservative group had a 23% crossover rate to catheterization, most commonly for worsening angina.
Impact on Clinical Practice
Guideline Impact
Limitations
Patients with left main disease were excluded after coronary CTA screening, limiting generalizability to that high-risk subgroup.
The 23% crossover rate from conservative to invasive may have diluted between-group differences.
Follow-up of 3.2 years may be insufficient to detect long-term survival differences, particularly in patients with extensive disease who may benefit from CABG.
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