CHICAGO – The case for survival equipoise between an invasive or conservative strategy for managing patients with stable coronary disease and moderate or severe cardiac ischemia grew stronger with an additional 2.5 years of median follow-up of the landmark ISCHEMIA trial.
During a median follow-up of 5.7 years in ISCHEMIA-EXTEND – and as long as 7 years – patients randomized to an upfront invasive strategy regardless of their symptoms had an all-cause mortality rate of 12.7%, compared with a 13.4% rate in the patients randomized to the conservative, medication-based management strategy that employed revascularization only when the medical approach failed to resolve their angina. This survival difference fell far short of significance (adjusted hazard ratio, 1.00; 95% confidence interval, 0.85-1.18), solidifying a finding first seen in the main ISCHEMIA results when they came out 3 years before, in late 2019, Judith S. Hochman, MD, said at the American Heart Association scientific sessions.
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Dr. Judith S. Hochman
The new results “provide evidence for patients with chronic coronary disease and their physicians as they decide whether to add invasive management to guideline-directed medical therapy,” concluded Dr. Hochman, professor and senior associate dean for clinical sciences at New York University Langone Health. Simultaneous with her report, the extended follow-up results also appeared in an article published online in Circulation.
Nil probability of a survival benefit
“The probability over 5.7 years that a patient’s risk of dying is lower with the invasive strategy is nil, which means: Go with the patient’s preference. Not undergoing revascularization is a reasonable strategy because there is no excess mortality,” Dr. Hochman said in an interview. The trial’s extended follow-up provides “much more robust evidence” for the neutral effect on survival. The investigators plan to further follow-up out to a maximum of 10 years to continue to monitor for a signal of a mortality difference.
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Dr. M. Cecilia Bahit
“These findings might help physicians in shared decision-making as to whether to add invasive management to guideline-directed medical management in selected patients with chronic coronary artery disease and moderate or severe ischemia,” commented M. Cecilia Bahit, MD, designated discussant for the report and chief of cardiology for INECO Neurosciences in Rosario, Argentina.
The original ISCHEMIA results had also shown that invasive intervention can improve the quality of life in patients who have angina as a result of their coronary disease, but also showed “minimal benefits” from an invasive approach in asymptomatic patients, who comprised 35% of the study cohort of 5,179 patients.
While ISCHEMIA enrolled patients with moderate to severe coronary ischemia identified with noninvasive testing, it excluded certain patients for whom an invasive strategy is recommended, including those with unprotected left main coronary stenoses of at least 50%, a recent acute coronary syndrome event, a left ventricular ejection fraction of less than 35%, more advanced functional limitations from heart failure, or advanced chronic kidney disease.
Follow-up without adjudication
The extended follow-up included 4,825 patients from the initial cohort, with data collected from 4,540 patients. One limitation of the follow-up was that the cause of death was not adjudicated as it had been during the initial follow-up phase. It instead relied on unconfirmed information collected either from patients’ families or national databases. The demographics and clinical profiles of the study participants available for extended follow-up closely matched the entire original study cohort.
The additional follow-up also revealed a significant survival benefit from the invasive approach for cardiovascular deaths, with an incidence of 8.6% in the conservative arm and 6.4% in the invasive group, an adjusted 22% relative reduction in this outcome favoring the invasive strategy (95% CI, 0.63-0.96). This difference had appeared as a nonsignificant signal in the initial 3.2-year median follow-up.
However, this significant benefit from the invasive strategy was counterbalanced by a surprising and inexplicable increase in deaths from noncardiovascular causes in those managed with the invasive strategy. Noncardiovascular deaths occurred in 5.5% of those in the invasive arm and in 4.4% of those in the conservative arm, a significant adjusted 44% relative increase in this outcome associated with invasive management. Again, this difference was not as clearly apparent after the initial follow-up phase.
“The increase in noncardiovascular deaths with the invasive strategy surprisingly persisted over time and offset” the cardiovascular survival benefit from upfront invasive treatment, explained Dr. Hochman. A prior report from the investigators looked in depth at the noncardiovascular deaths during the initial follow-up phase and found that most of the excess was caused by malignancies, although why this happened in the invasively treated patients remains a mystery.