Johan Vandenbogaerde

Delayed restoration of atrial function after conversion of atrial flutter by pacing or electrical cardioversion

It is often suggested but never proven that atrial function is not affected during atrial flutter, nor after its conversion to normal sinus rhythm. To evaluate this hypothesis, a prospective study was performed in 22 patients (age range 20 to 88 years) with atrial flutter. Diastolic transmitral flow was analyzed with echo-Doppler before and after conversion. After randomization, conversion was attempted with overdrive pacing or up to two 50 J shocks. If the initial method was unsuccessful, a 200 J shock was administered. All patients were converted to sinus rhythm with this protocol. Shortly after conversion (at 1 and 6 hours), atrial contribution to ventricular filling was absent in 4 of 22 patients. In the remaining 18 patients, atrial contribution to ventricular filling was small. Atrial contribution to transmitral flow improved from 20 to 27% within 24 hours (p < 0.01) and increased further to 38% at 6 weeks (p < 0.005). Peak velocity of late diastolic filling increased from 0.28 m/s after 1 hour to 0.39 m/s after 24 hours (p < 0.0001) and improved even further during later follow-up. In 1 patient, an effective atrial systole was not observed until the 14th day. Cardiac output did not change significantly during the study period. No differences were observed between the conversion modalities. In conclusion, atrial dysfunction is present immediately after conversion of atrial flutter to normal sinus rhythm. This dysfunction occurs also after overdrive pacing and can last > 1 week. The findings suggest that stasis in the atria can remain temporarily present after successful conversion of atrial flutter to sinus rhythm.

Use of dopexamine hydrochloride in patients with septic shock.

The short and long-term hemodynamic effects of iv dopexamine hydrochloride (DPX) were studied in ten patients with septic shock. In the short-term study, a dose-dependent increase in cardiac index and heart rate, and a dose-dependent decrease in systemic vascular resistance were demonstrated. These effects diminished gradually during the long-term study, suggesting a problem of tolerance. Although the administration of DPX during septic shock appeared to be relatively safe, its hemodynamic effects suggest that it may be more indicated in selected patients with a low cardiac output.

Use of dopexamine hydrochloride in intensive care patients with low-output left ventricular heart failure.

The short- and long-term hemodynamic effects of intravenous dopexamine hydrochloride (Dopacard) were studied in 12 patients with low cardiac output left ventricular heart failure. In the short-term study, a dose of 4 micrograms/kg/min produced a 60% increase in cardiac output (p less than 0.001), a 30% increase in stroke volume (p less than 0.01), a 23% increase in heart rate (p less than 0.01) and a 39% decrease in systemic vascular resistance (p less than 0.001). In the long-term study, there was a sustained hemodynamic benefit after 8 hours of dopexamine hydrochloride infusion (mean dose 3.5 micrograms/kg/min). There was a 32% increase in cardiac output (p less than 0.001), an 18% increase in stroke volume (p less than 0.05), a 12% increase in heart rate (p less than 0.001) and a 30% decrease in systemic vascular resistance (p less than 0.01). After 48 hours of dopexamine hydrochloride infusion (mean dose 3.8 micrograms/kg/min), the hemodynamic effect was significant only for cardiac output (+20%, p less than 0.05) and for systemic vascular resistance (-26%, p less than 0.01). Thus, dopexamine hydrochloride has beneficial short-term hemodynamic effects in patients with low-output left ventricular heart failure and the benefit appears to diminish with long-term infusion.

The initial clinical evaluation of a transesophageal system with pulsed Doppler, continuous wave Doppler, and color flow imaging based on an annular array technology

The application of transesophageal echocardiography (TEE) offers access to a great deal of important clinical information regarding cardiovascular anatomy and physiology. Two applications which have not been reported and would appear to be of interest are continuous wave Doppler capabilities and the implementation of higher frequency transducers. A TEE system designed at the Institute of Biomedical Engineering in Trondheim, which is based on an annular array technology, offers these capabilities. We evaluated this instrument in the clinical setting in a series of 30 patients to test the probe function in terms of the tissue and flow imaging quality with a 7.5 MHz carrier frequency, and to report on the implementation of a continuous wave Doppler modality in a TEE probe. We found that the annular array method permitted the use of high frequency probes for tissue and flow imaging which resulted in excellent image resolution, and that shifting the carrier frequency of the transducer to a lower frequency permitted the optimization of the Doppler sensitivity. The continuous wave Doppler was used to measure abnormal blood flow velocities in excess of 5.0m/s, and was particularly useful in the operating room as velocity measurements could be obtained without compromising the sterile field. The results of our evaluation indicate that high imaging frequencies and continuous wave Doppler can be applied by an annular array TEE transducer.