VANQWISH Trial Results
ABSTRACT & COMMENTARY
Synopsis: The authors of the VANQWISH trial on invasive vs. conservative strategy conclude that a routine early invasive strategy in non-Q MI patients worsens short-term outcome.
Source: Boden W. Veterans Affairs Non-Q Wave Infarction Strategies In-Hospital Trial. Presented at American College of Cardiology annual scientific sessions. March 16-18, 1997.
On march 18, 1997, at the american college of Cardiology Annual Scientific Session in Anaheim, California, the initial results of the Veterans Affairs Non-Q Wave Infarction Strategies In-Hospital (VANQWISH) trial were presented by the principle investigator, William Boden, MD. The rationale for the study was to test the widely-held view that because of the high risk for subsequent events in non-Q MI patients that an invasive strategy (coronary angiography followed by myocardial revascularization, if feasible) would yield better short- and long-term outcomes than a conservative strategy (radionuclide ventriculogram and predischarge thallium exercise test) with application of revascularization only in those with inducible ischemia or an unstable clinical course.The primary end point of this randomized minimal 12-month follow-up study was all-cause mortality plus non-fatal infarction. Investigators at 15 VA Medical Centers identified 2738 patients with non-Q MI. After excluding patients with severe concomitant disease, 1450 remained protocol eligible, of whom 920 agreed to randomization. (One-third of the total population, two-thirds of the protocol eligible patients.) Baseline clinical characteristics in the two strategies were well-matched, with the exception of ejection fraction, which was higher (53% vs 50%; P < 0.01) in the invasive arm. The primary end point (death + MI) was 7.8% in the invasive arm and 3.3% in the conservative arm (P = 0.01) before hospital discharge and was 22% vs 23% at one year. The primary end point was driven by death, not by MI, since the pre-discharge death rate was 4.5% invasive vs. 1.3% conservative and the one year rate was 13% vs. 12%; MI was not statistically different at any time. If death at one month is separated from in-hospital and one-year death rates, it is evident that most of the excess deaths occur early (1 month) in the invasive strategy (discharge 4.6% vs 1.3%, P = 0.01; one month 5% vs 2%; P = 0.03; one year 13% vs 8%; P = 0.06), suggesting a relationship to the invasive procedure. In the invasive arm, there was no difference in the primary end point between those who did or did not undergo revascularization, whereas in the conservative arm, those who crossed over to revascularization did have a higher event rate (35% vs 23%; P = < 0.001). The authors conclude that a routine early invasive strategy in non-Q MI worsens short-term outcome.
COMMENT BY MICHAEL H. CRAWFORD, MD
Boden was quoted in the press as saying, "The bottom line is: stabilize the patient, treat the patient with non-invasive testing and medication, and then if you’re going to pursue the revascularization route, do so selectively." Or, follow the conservative strategy of this trial that Boden has referred to as the more intuitive approach where "treatment is dependent upon objective clinical findings rather than a reflex decision to catheterize all non-Q wave patients, even those who are at low risk." Indeed non-Q MI patients who meet the inclusion and exclusion requirements for this study were a low-risk group since their in-hospital mortality rate was 1.3%. It is going to be hard to beat that rate with any other strategy, and in this trial, the invasive course tripled the mortality. Exclusion criteria included high-risk patients who could not be stabilized because of ongoing ischemia, hemodynamic instability, or incessant arrhythmias. Also excluded were those with severe concomitant disease, recent revascularization and those with left bundle branch block on ECG. All others were considered protocol eligible. So, triage to the lower risk group in this study was based upon straightforward clinical information.Of interest, the number of crossovers from the conservative strategy to revascularization for definite indications was about one-third in VANQWISH. This is much lower than the rate of two-thirds in the Thrombosis In Myocardial Infarction (TIMI) III trial that studied unstable angina patients, one-third of whom had non-Q MI (inclusive definition of unstable angina). Either the unstable angina component of the TIMI group occasioned the high number of crossovers to an invasive approach or the non-Q group was at high risk vs. the VANQWISH patients. TIMI III suggests that an early invasive approach may be preferable in unstable angina, but VANQWISH data would argue that the non-Q MI subgroup should be treated more conservatively.
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