Transient left posterior hemiblock during myocardial ischemia-eliciting exercise treadmill testing: a report of a case and a critical analysis of the literature.

We describe a 75-year-old male patient with two-vessel coronary artery disease, who developed transient left posterior hemiblock (LPH) while undergoing an exercise treadmill test (ETT). The intraventricular conduction abnormality initially had the features of alternating LPH, which evolved to stable LPH prior to dissipating, and it occurred at the first minute of recovery. The exercise electrocardiogram and the associated thallium-201 myocardial perfusion scintigraphy (Tl) revealed severe reversible myocardial ischemia. This rare occurrence is discussed in the context of the observed coronary lesions, the distribution of the radionuclide-detected ischemia, and the previous experience from the literature. An insight regarding the low prevalence of transient LPH is afforded, since the described case derives from a series of 2,160 consecutive patients who underwent ETT in conjunction with Tl. Finally, a comment is provided on the complexities of deciphering the specific pathophysiologic mechanism(s) of transient LPH, occurring during ETT.