Acute evaluation of a preformed single-pass VDD/DDD pacing lead.

The clinical utility of single lead, atrial synchronous, ventricular pacing (VDD), for patients with normal sinus function and heart block is well established. Atrial stimulation, unavailable in VDD systems presents a significant disadvantage. DDD pacing systems however, require the introduction and positioning of two separate leads. The acute human study discussed evaluated a modified version of a commercially available VDD lead with a preshaped lobe, capable of both sensing and pacing the right atrium. "P" waves and atrial stimulation thresholds were determined in five patients. The mean P-wave was 2.5 +/- 1 millivolts. Atrial stimulation in the unipolar configuration was 1.6 +/- 0.5 volts and 1.7 +/- 0.9 volts in the bipolar configuration. These acute stimulation thresholds and sensing amplitudes were comparable to conventional DDD pacing systems. Therefore, single-lead DDD pacing may be feasible and warrants further study.

Bilateral coronary thrombosis in the absence of inducible coronary spasm, thrombocytosis, coagulation abnormalities, or angiographic evidence of coronary artery disease: previously undescribed method of myocardial infarction.

A 32-year-old man presented with symptoms and electrocardiographic changes consistent with acute anterolateral myocardial infarction. Selective coronary angiography revealed thromboses in the infarct related artery as well as in the right coronary artery. This case is unique because bilateral in-situ coronary thrombosis producing acute myocardial infarction was documented in the absence of previously proposed mechanisms.