New England Journal of Medicine April 09, 2020

Initial Invasive or Conservative Strategy for Stable Coronary Disease

David J. Maron, Judith S. Hochman, Harmony R. Reynolds, Sripal Bangalore, Sean M. O'Brien, William E. Boden, et al.

Bottom Line

In patients with stable coronary disease and moderate to severe ischemia, an initial invasive strategy did not significantly reduce the risk of ischemic cardiovascular events or death compared to an initial conservative strategy of optimal medical therapy.

Key Findings

1. Over a median follow-up of 3.2 years, the primary composite outcome occurred in 318 patients in the invasive-strategy group and 352 in the conservative-strategy group, showing no significant overall difference.

2. At 6 months, the cumulative primary event rate was higher in the invasive group (5.3% vs. 3.4%; difference, 1.9 percentage points; 95% CI, 0.8 to 3.0), largely driven by periprocedural myocardial infarctions.

3. At 5 years, the cumulative primary event rate crossed over, becoming slightly lower in the invasive group (16.4%) compared to the conservative group (18.2%) (difference, -1.8 percentage points; 95% CI, -4.7 to 1.0).

4. All-cause mortality was nearly identical between the groups, with 145 deaths in the invasive-strategy group and 144 deaths in the conservative-strategy group (Hazard Ratio 1.05; 95% CI, 0.83 to 1.32).

Study Design

Design

RCT

Open-Label

Sample

5,179

Patients

Duration

3.2 yr

Median

Setting

37 countries

Population Patients with stable coronary artery disease and moderate or severe ischemia on stress testing.

Intervention Initial invasive strategy consisting of routine coronary angiography and revascularization (PCI or CABG) when feasible, plus optimal medical therapy.

Comparator Initial conservative strategy consisting of optimal medical therapy alone, with angiography and revascularization reserved for failure of medical therapy.

Outcome Composite of death from cardiovascular causes, myocardial infarction, or hospitalization for unstable angina, heart failure, or resuscitated cardiac arrest.

Study Limitations

• The open-label design could have introduced bias, particularly for subjective components of the primary endpoint such as hospitalization for unstable angina.

• Patients with left main coronary disease, left ventricular ejection fraction < 35%, recent acute coronary syndrome, or unacceptable levels of angina were excluded, limiting the generalizability of the findings to these high-risk populations.

• The primary composite endpoint was expanded during the trial (adding hospitalization for heart failure and resuscitated cardiac arrest) due to slower-than-expected overall event rates.

• The findings were highly sensitive to the definition of myocardial infarction used; an invasive strategy increased periprocedural MIs but decreased spontaneous MIs.

• Median follow-up was relatively short (3.2 years); given that event curves crossed at approximately 2 years, longer-term follow-up may be necessary to fully capture late clinical benefits.

Clinical Significance

The ISCHEMIA trial fundamentally shifted the management paradigm for chronic coronary syndromes. It established that for stable patients with preserved ventricular function—even those with moderate-to-severe ischemia—an initial conservative approach using intensive optimal medical therapy is safe and effective. Routine invasive angiography and revascularization do not prolong life or prevent future myocardial infarctions in this population. Consequently, invasive management should be appropriately reserved for patients whose angina symptoms remain unacceptable despite optimal medical therapy or for those who develop acute coronary syndromes.

Historical Context

For decades, it was widely believed that routine revascularization (PCI or CABG) reduced the risk of myocardial infarction and death in patients with stable coronary artery disease. The landmark COURAGE trial (2007) challenged this notion, showing no prognostic benefit for PCI over medical therapy. However, COURAGE was criticized because patients underwent angiography before randomization (allowing clinicians to exclude high-risk anatomy) and many did not have significant ischemia. The 'ischemia hypothesis' posited that a subgroup of patients with documented moderate-to-severe ischemia would indeed benefit from revascularization. Designed to address this directly, the ISCHEMIA trial required stress testing before randomization and blinded the anatomic data. Its results firmly debunked the ischemia hypothesis, confirming and extending the findings of COURAGE.

Guided Discussion

High-yield insights from every perspective

Med Student

Medical Student

How does the pathophysiology of stable angina differ from acute coronary syndrome, and why might this explain why an invasive strategy (stenting or CABG) did not prevent future myocardial infarctions or death in stable CAD patients as seen in the ISCHEMIA trial?

Key Response

This tests the foundational understanding of plaque stability. Stable CAD is typically driven by flow-limiting, thick-capped fibroatheromas that cause exertional ischemia but are relatively stable. Acute coronary syndrome (ACS) is usually caused by the sudden rupture or erosion of non-obstructive, thin-capped vulnerable plaques. Stenting a stable lesion relieves ischemia and angina symptoms but does not alter the systemic biology of vulnerable plaques that cause future spontaneous MIs, which is why optimal medical therapy (statins, antiplatelets) is the cornerstone for mortality and MI reduction.

Resident

A 65-year-old patient with stable exertional angina and a positive stress test (moderate ischemia) asks if they need a stent. Based on the ISCHEMIA trial, how should you counsel them regarding the benefits of optimal medical therapy versus an invasive approach?

Key Response

Residents must apply trial data directly to patient counseling. The rationale should highlight that an initial conservative approach with optimal medical therapy (OMT) is equally effective for preventing death and MI compared to an invasive strategy. However, the invasive strategy provides superior symptom relief and quality of life improvements specifically for patients who have frequent or unacceptable angina despite medical therapy. The decision to revascularize should be framed as a symptom-driven choice, not a survival-driven one.

Fellow

The ISCHEMIA trial required a blinded coronary CT angiography (CCTA) before randomization for the majority of patients. How did this crucial step alter the study population compared to prior trials like COURAGE, and how does it influence the way we apply these results in real-world cardiology practice?

Key Response

Fellows must grasp the nuances of trial design and patient selection. The blinded CCTA was used to exclude patients with unprotected left main disease (who have a known mortality benefit from revascularization) and those with non-obstructive CAD. This makes the trial's safety findings for the conservative arm robust, but it strictly implies that in real-world practice, clinicians must first reliably rule out left main disease (via CCTA or other means) before confidently committing a patient with moderate-to-severe ischemia to a strictly conservative OMT pathway.

Attending

The ISCHEMIA trial demonstrated a crossover in the Kaplan-Meier curves for the primary endpoint, showing early harm (increased periprocedural MI) but late benefit (reduction in spontaneous MI) in the invasive arm. How should we weigh these competing risks when discussing long-term prognosis and treatment durability with our patients?

Key Response

Attendings deal with complex risk/benefit discussions and long-term outcomes. While early periprocedural MIs (Type 4a/5) are often biomarker-driven and generally carry a less severe long-term prognosis than spontaneous MIs (Type 1), the overall net clinical benefit for hard endpoints remained neutral at 3 to 5 years. This teaches us to balance the upfront procedural risks against the potential for durable freedom from spontaneous events, using shared decision-making centered on the patient's immediate symptom burden and risk tolerance.

Scholarly Review

Critical appraisal through the lens of expert reviewers and guideline development

PhD

The ISCHEMIA investigators altered the primary endpoint during the trial from a 3-component composite (CV death, MI, resuscitated cardiac arrest) to a 5-component composite (adding hospitalization for unstable angina or heart failure) due to slower-than-expected event rates. What are the statistical and methodological implications of expanding a composite endpoint mid-trial, and how does it impact the interpretation of the null hypothesis?

Key Response

This addresses expert-level research methodology. Changing endpoints mid-trial (even if blinded to treatment allocation) is done to preserve statistical power and avoid an underpowered study. However, expanding a composite endpoint by adding 'softer' endpoints (like hospitalization for unstable angina) dilutes the clinical gravity of the primary outcome. A PhD critique would focus on whether the treatment effect is driven primarily by the softer components, alpha spending, and how this impacts the validity and generalizability of the final neutral conclusion.

Journal Editor

As a reviewer, how would you critically appraise the ISCHEMIA trial's reliance on combining different definitions of myocardial infarction (e.g., periprocedural vs. spontaneous) into a single primary endpoint, and does the differential prognostic weight of these MI types threaten the validity of the trial's conclusions?

Key Response

Editors focus on measurement bias and endpoint definitions. Combining Type 1 (spontaneous) and Type 4a/5 (periprocedural) MIs into a single composite endpoint is controversial because they carry vastly different mortality risks. A tough reviewer would flag that an excess of 'mild' periprocedural MIs in the invasive arm could statistically mask a true and clinically meaningful reduction in 'severe' spontaneous MIs. Appraising how the authors handled secondary analyses separating these MI types is critical for evaluating the paper's ultimate editorial significance.

Guideline Committee

In light of the ISCHEMIA trial's findings, how should clinical practice guidelines update their Class of Recommendation for routine revascularization in patients with stable ischemic heart disease (SIHD), and how does this elevate the recommended role of CCTA in the diagnostic algorithm?

Key Response

Guidelines focus on translating evidence into standardized practice. ISCHEMIA reinforced a Class I recommendation for Guideline-Directed Medical Therapy (GDMT) as first-line therapy for SIHD and downgraded the routine use of revascularization for survival benefit, reserving it primarily for symptom control (Class I/IIa depending on angina severity). Furthermore, it strongly supports elevating CCTA to a Class 1 recommendation (as seen in the 2021 AHA/ACC Chest Pain guidelines) as a front-line tool to safely rule out high-risk anatomy (e.g., left main disease) before pursuing a conservative strategy.

Clinical Landscape

Noteworthy Related Trials

2007

COURAGE Trial

n = 2,287 · NEJM

Tested

PCI + Optimal Medical Therapy (OMT)

Population

Patients with stable coronary artery disease

Comparator

OMT alone

Endpoint

Death from any cause and nonfatal myocardial infarction

Key result: As an initial management strategy in patients with stable coronary artery disease, PCI did not reduce the risk of death, myocardial infarction, or other major cardiovascular events when added to optimal medical therapy.

2009

BARI 2D Trial

n = 2,368 · NEJM

Tested

Prompt revascularization (PCI or CABG) + intensive medical therapy

Population

Patients with type 2 diabetes and stable CAD

Comparator

Intensive medical therapy alone

Endpoint

Death from any cause

Key result: There was no significant difference in the rates of death and major cardiovascular events between patients undergoing prompt revascularization and those undergoing medical therapy.

2017

ORBITA Trial

n = 200 · Lancet

Tested

PCI

Population

Patients with severe single-vessel coronary disease and stable angina

Comparator

Sham procedure (placebo)

Endpoint

Difference in exercise time increment

Key result: In patients with medically treated angina and severe coronary stenosis, PCI did not increase exercise time significantly more than a sham procedure.

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