Results from this prospective study of the Wavelet electrogram morphology discrimination algorithm operating as the sole discriminator in the ON mode demonstrate that inappropriate therapy for supraventricular tachycardia in a single-chamber ICD can be dramatically reduced compared to rate detection alone.
The hemodynamic effects of intravenously administered adenosine, a potent vasodilator, were examined in 15 patients with pulmonary hypertension. All patients were given adenosine, 50 micrograms/kg per min, increased by 50 micrograms/kg per min at 2 min intervals to a maximum of 500 micrograms/kg per min or until the development of untoward side effects. The patients were then given oral nifedipine, 20 mg every hour, until a greater than or equal to 20% decrease in pulmonary vascular resistance or systemic hypotension occurred. The administration of maximal doses of adenosine, 256 +/- 46 micrograms/kg per min, produced a 2.4% reduction in pulmonary artery pressure (p = NS), a 37% decrease in pulmonary vascular resistance (p less than 0.001) and a 57% increase in cardiac index (p less than 0.001). The administration of maximally effective doses of nifedipine (91 +/- 36 mg) produced a 15% reduction in the mean pulmonary artery pressure (p less than 0.05), a 24% decrease in pulmonary vascular resistance (p less than 0.01) and an 8% increase in cardiac index (p = NS). There was a significant correlation (r = 0.714, p = 0.01) between the reduction in pulmonary vascular resistance that resulted from adenosine administration and that achieved with the administration of nifedipine. Six patients had substantial reductions in pulmonary vascular resistance with adenosine but not with nifedipine. Thus, adenosine is an effective vasodilator in patients with pulmonary hypertension and can be used for safe and rapid assessment of vasodilator reserve in these patients.(ABSTRACT TRUNCATED AT 250 WORDS)
Within the acceptable noise range for SAECG, lower noise results in longer QRSd and larger variance, suggesting that more accurate recordings may have less reproducibility. The random timing of noise relative to signal results in the distribution/variance of repeated measurements. Statistical strategies may be used to reduce some of this variance and may enhance the diagnostic utility of SAECG.
Adenosine has the ability to further decrease pulmonary artery pressure and pulmonary vascular resistance in patients with primary pulmonary hypertension who respond to calcium channel blockers. Those who fail to respond to these agents have little added effect from adenosine.
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