Background: Myocardial ischemia causes accumulation of extracellular myocardial K+ ([K+]e). However, the relation between [K+]e, and local coronary venous K+, i.e., K+ in the great coronary vein ([K+]gcv) has not been established. To determine the sensitivity of [K+]gcv as a marker of myocardial ischemia, we continuously measured [K+]e, using intramyocardial K+-selective plunge electrodes, and [K+]gcv, using a catheter-tip K+ electrode inserted into the great cardiac vein, during two types of ischemia. Methods and Results: In in-situ pig hearts, ischemia was induced by implementing a progressive decrease in carotid-to-left anterior descending artery (LAD) shunt flow from 40 to 0 mL/min at constant heart rate (100-130/min) and a progressive increase in heart rate from 100 to 160 beats/min at the threshold flow. The progressive decrease in LAD flow to 5 mL/min caused parallel increases in [K+]e (from 3.87 ± 0.37 to 8.65 ± 1.13 mM) and [K+]gcv (from 3.87 ± 0.37 to 4.84 ± 0.43 mM). However, below 5 mL/min, [K+]gcv failed to reflect the increase in [K+]e and often decreased. The progressive increase in heart rate at the threshold flow caused parallel changes in [K+]e (from 4.08 ± 0.36 to 4.87 ± 0.14 mM, n = 3) and [K+]gcv (from 3.08 ± 0.42 to 4.18 ± 0.43 mM). The verapamil- and propranolol-induced changes in [K+]e during low-flow ischemia were reflected by changes in [K+]gcv. Conclusions: Change in [K+]gcv is a sensitive marker of myocardial ischemia, except at very low coronary flow. Thus, [K+]gcv can be used to detect early myocardial ischemia.
Background: Complex electrocardiogram morphologies (atrial fibrillation [AF] nests) in sinus rhythm (SR) recorded by frequency domain techniques can serve as a pathologic substrate for atrial fibrillation (AF). We sought to characterize any direction-dependent and rate-dependent changes in dominant frequency (DF) and high DF sites in the left atrium (LA) in patients with AF. Methods: Eight patients with AF were included in the study. A basket catheter with 64 electrodes was placed in the LA. Forty-eight bipolar electrocardiograms were recorded during SR and during pacing from the high right atrium (HRA), proximal coronary sinus (CS), and distal CS at various pacing rates, ranging from 600 ms to 250 ms. The frequency domain measures of LA bipolar electrocardiograms were compared during SR and HRA, proximal CS, and distal CS. Results: The DF was found to be higher during proximal CS and distal CS pacing than during SR. The percentage of high DF (>70 Hz) sites was higher during distal CS pacing than during SR. The various pacing rates applied during HRA, proximal CS, and distal CS pacing did not affect the DF values. Conclusion: DF of atrial electrocardiograms obtained during SR was influenced by the direction of conduction but not by the pacing rate.