Prognostic value of microvolt T wave alternans and risk stratification of dilated cardiomiopathy

Authors:
G. Molon¹, A. Costa¹, T. De Santo², G. Ligorio¹, E. Barbieri², ¹S Cuore Hospital - Negrar - Italy, ²medtronic italy - Milano - Italy,

Topic(s):
Non invasive studies

Citation:
European Heart Journal ( 2007 ) 28 ( Abstract Supplement ), 409

Introduction: Many patients (pts) included in MADIT-II, MUST and SCD-HeFT studies, likely to undergo automatic Implantable Cardioverter Defibrillator (ICD) implant in primary prevention of Sudden Death (SD), will actually never experience hazardous ventricular arrhythmias. Microvolt T Wave Alternans (MTWA) is a useful noninvasive diagnostic tool used in risk stratification of pts with cardiomyopathy and poor venticular function (DCM) approved by US FDA and by ACC/AHA/ESC 2006 Guidelines (JACC 2006; 48: 247-346) in management of pts with ventricular arrhythmias and prevention of SD (Class IIa - level of evidence A).

Aim of the study: To define clinical and prognostic value of MTWA in pts of our Department with DCM indicated for ICD implant in primary prevention and to compare our results with other studies using MTWA in similar populations of pts.

Methods: 152 consecutive pts underwent MTWA; mean EF was 31±8%. Median Follow Up (FU) 456 days; mean age 65±9 years, 122 males (80%), BMI 27±4; previous MI in 26%; Hypertension in 81 pts (53%) and Diabetes in 31 pts (20%). Class NYHA II-III was present in 85%. During FU we considered all-cause mortality, and documentation of hazardous ventricular arrhythmias (sustained VT; VF).

Results: MTWA was normal in 41 pts (27%), abnormal in 111 pts (73% - 59% positive and 14% indeterminate). The average onset, in positive tests, was 95±9 bpm. 75/111 (68%) pts with abnormal TWA and 7/41 (17%) pts with normal TWA had successful ICD implant. During FU period 6 deaths occurred in pts with abnormal MTWA vs no death in pts with normal MTWA; there were also 21 pts with hazardous ventricular arrhythmias among those with abnormal MTWA and only 1 in pts with normal MTWA. The combined end-point "death + hazardous ventricular arrhythmias" was significantly higher (p=0.01) in pts with abnormal MTWA. Test sensitivity in risk stratification was 95% (21 pts/22) and Negative Predictive Value (NPV) was 98% (40pts/41); on the contrary specificity was 31% (40 pts/130) and Positive Predictive Value (PPV) was 19% (21pts/111).

Conclusions: Our analysis confirms that MTWA may help to identify a lower risk group in pts with DCM, like most important studies that quote NPV of this test higher than 90%. MTWA is a non-invasive, low expensive test that appears to be a promising technique to separate high-risk pts from low-risk pts. This could be, when assessed by further larger studies, a useful tool to reduce the number of pts to threat with ICD implant in order to optimize correct utilization of healthcare resources.