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An ischemic index from the electrocardiogram to select patients with low left ventricular ejection fraction for
T Hinohora1, N B Wagner, F R Cobb
1Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710.
Insights
Patients with low left ventricular ejection fraction (LVEF) may benefit from coronary artery bypass grafting (CABG) if their condition is due to reversible ischemia. A high "ischemic index" identifies candidates likely to see improved LVEF post-surgery.
Area of Science:
- Cardiology
- Cardiac Surgery
- Diagnostic Imaging
Background:
- Decreased left ventricular ejection fraction (LVEF) often leads to denial of coronary artery bypass grafting (CABG).
- This denial is based on the assumption that low LVEF is irreversible, typically due to myocardial necrosis.
- However, if low LVEF results from both necrosis and ischemia, CABG may improve cardiac function.
Purpose of the Study:
- To develop and validate a method for identifying patients with low LVEF who may benefit from CABG.
- To determine if an "ischemic index" can predict improvement in LVEF after CABG.
Main Methods:
- An "ischemic index" was calculated for 37 patients.
- The index was derived from the difference between LVEF estimated by Selvester QRS score (necrosis) and LVEF measured by radionuclide angiography (necrosis + ischemia).
Main Results:
- Patients with an ischemic index ≥ 11 showed a mean LVEF increase of 5% (p=0.02) post-CABG.
- Those with an index ≤ 0 experienced a mean LVEF decrease of 8% (p=0.02).
- Patients with an index between 0 and 10 had no significant change in LVEF.
Conclusions:
- A high "ischemic index" suggests reversible ischemia and predicts improved LVEF after CABG.
- This index can help identify suitable candidates for CABG among patients with depressed LVEF.
- The findings support re-evaluating CABG eligibility for patients with low LVEF based on ischemic burden.
Abstract:
Patients who have a decreased left ventricular (LV) ejection fraction (EF) may be denied coronary by-pass grafting (CABG) because it is assumed that improvement in function is unlikely. If the low LVEF were due to myocardial necrosis, this assumption would be valid. If the dysfunction were due to both necrosis and ischemia, however, then improvement may be possible with CABG. A method capable of identifying such patients would be useful. In this study, an "ischemic index" was determined for 37 patients based on the difference between the presurgical LVEF estimated from the standard 12-lead electrocardiogram by the Selvester QRS score (indicating the extent of dysfunction due to necrosis) and the presurgical LVEF measured from resting multigated radionuclide angiography (indicating dysfunction due to both necrosis and ischemia). It was hypothesized that a high ischemia index, that is, a large discrepancy between estimated and measured LVEF, would be associated with an improved post-surgical measured LVEF. The results showed that patients with an ischemic index of less than or equal to 0 had a mean decrease in LVEF of 8% (p = 0.02) and those with an index between 0 and 10 had no mean change. Patients with an index greater than or equal to 11, however, had a mean increase of 5% (p = 0.02), suggesting that depressed LVEF may improve following CABG among patients whose low function is due primarily to reversible ischemia as indicated by a high ischemic index.