What Can Ischemia and Ventricular Tachycardia Tell Us about Cardiovascular Risk?

James Harkness, from the TIMI Study Group at Brigham and Women's Hospital, presented results from "Presence of Ischemia and Non-sustained Ventricular Tachycardia is Strongly Associated with the Risk of Cardiovascular Outcomes: Observations from the MERLIN-TIMI 36 Trial" during an abstract oral session at the American Heart Association Scientific Sessions 2009. The study looked at the risk of ischemia and nonsustained ventricular tachycardia (NSVT) alone or combined in patients with non-ST-segment elevation acute coronary syndrome (NSTE-ACS).

The Metabolic Efficiency with Ranolazine for Less Ischemia in Non-ST-Elevation Acute Coronary Syndrome (MERLIN)-Thrombolysis in Myocardial Infarction (TIMI) 36 (MERLIN-TIMI 36) trial randomized 6,560 patients hospitalized with a NSTE-ACS to ranolazine or placebo in addition to standard therapy. For the purposes of this study, ischemia was defined as greater than 1mm ST depression that lasted for more than one minute, and NSVT was defined as more than four consecutive ventricular beats.

In the current study, 6,355 patients with NSTE-ACS were monitored on seven-day continuous ECG (Holter monitor) with median follow-up of 348 days. Patients were categorized into four groups: no NSVT or ischemia; ischemia alone; NSVT alone; or ischemia plus NSVT.

The researchers reported that 43% of patients had no NSVT or ischemia; 18.5% had ischemia alone; 31% had NSVT alone; and 6.8% had NSVT plus ischemia.

One-year clinical outcomes show that patients with recurrent ischemia alone faced an increased risk for all CV outcomes compared to patients with no NSVT or ischemia (CV death: 6.1% vs. 3%; SCD: 2.6% vs. 0.9%; MI: 11.8% vs. 6.2%; recurrent ischemia: 17.2% vs. 9.7%; and heart failure: 5.9% vs. 3%).

Patients with NSVT alone faced an increased risk of CVD, SCD, and subsequent heart failure compared to patients with no NSVT or ischemia: (CV death: 4.3% vs. 3%; SCD: 2.2% vs. 0.9%; MI: 7.2% vs. 6.2%; recurrent ischemia: 9.4% vs. 9.7%; and heart failure: 5.6% vs. 3%).

Patients with NSVT and ischemia faced an increased risk for CVD, SCD, recurrent MI, and heart failure compared to patients with no NSVT or ischemia: (CV death: 10.1% vs. 3%; SCD: 7.8% vs. 0.9%; MI: 15.4% vs. 6.2%; recurrent ischemia: 18.8% vs. 9.7%; and heart failure: 13% vs. 3%).

The authors conclude:

In patients with NSTE-ACS, the presence of ischemia or NSVT detected on seven-day continuous ECG is independently associated with poor CV outcomes.

Patients with NSVT and ischemia are at particularly high risk for CVD and SCD, especially within the first weeks following ACS.

The addition of NSVT and ischemia to known CV risk factors significantly improves discrimination and risk reclassification for CVD and SCD.

Continuous ECG monitoring after NSTE-ACS identifies high-risk patients who may benefit from early treatment to prevent SCD, such as ICD implantation or LifeVest wearable defibrillators.