BACKGROUND: Perhexiline improves functional capacity in heart failure, but the mechanisms are undefined. We sought its effects on myocardial deformation in patients with viable myocardium. METHODS: Thirty-six medically-treated patients, stable at least 6 months post-infarction with LV dysfunction and myocardial viability shown by dobutamine echo (DbE) were randomised to receive perhexiline or matching placebo for 1 year. Cardiopulmonary exercise testing and DbE were performed at baseline and follow-up. Peak-systolic strain (S) and strain rate (SR) were measured offline in 111 dysfunctional segments in the placebo and 88 in the treatment group at rest, low-dose (LDD) and peak-dose dobutamine (PDD). RESULTS: The serum perhexiline level was 0.27+/-0.7 microg/l. There was no difference in the wall motion response to dobutamine at baseline and follow-up. Resting strain and SR were similar in the two groups at baseline and follow-up. However, SR at LDD and PDD increased in the placebo group and worsened during the same period in the perhexiline group. Patients on perhexiline and placebo had a similar rate-pressure product and exercise duration at baseline (7.9+/-2.7 vs 8.7+/-3.3 min, p=NS) and follow-up (9.6+/-4.6 vs 10.1+/-3.03 min, p=NS). CONCLUSION: Perhexiline does not improve the deformation of abnormal myocardial segments in patients with ischaemic LV dysfunction.