Influence of short atrioventricular delay on late diastolic transmitral flow and stroke volume.

Atrial transport function and the corresponding transmitral flow and stroke volume depend on the timing of atrial contraction. To study the influence of short atrioventricular delay (AVD) on these hemodynamic parameters, transmitral flow velocity (by pulsed wave Doppler) and aortic flow (by electromagnetic technique) were studied and compared (paired t test) during normal and short AVD at fixed rate DDD pacing (80 bpm) in AV-blocked, open-chest canine preparations (n:16). The short AVD resulted in a shorter acceleration (difference 4.1 +/- 4.9 msec, mean +/- SD, p less than 0.05), a lower peak velocity (difference: 7.1 +/- 3.2 cm/sec, p less than 0.001), a shorter (difference: 26.9 +/- 16.2 msec, p less than 0.001) and more rapid deceleration (difference: 220.7 +/- 291.7 cm/sec2, p less than 0.005) of the late diastolic transmitral flow elicited by atrial systole. Stroke volume decreased (7.8 +/- 5.2%, p less than 0.001) during short AVD as a consequence of a reduced left ventricular filling due to the interruption of the active atrial transport by the onset of the ventricular contraction.

Effect of superoxide dismutase on infarct size and postischemic recovery of myocardial contractility and metabolism in dogs.

The effects of superoxide dismutase treatment on infarct size, postischemic recovery of contractile function and tissue content of high energy phosphates were examined in a canine model of myocardial ischemia and reperfusion. Ischemia was induced by thrombotic occlusion of a coronary artery and reperfusion was achieved by intravenous thrombolysis. Average duration of ischemia was 90 min. Fifty closed chest anesthetized dogs were randomized to receive either superoxide dismutase (34,000 IU/min intravenously) or placebo, starting approximately 30 min before and continuing for 30 min into the reperfusion phase. Left ventricular ejection fraction and regional segmental shortening of the postischemic area were calculated from contrast angiograms after 4 h, 48 h and 1 week of reperfusion. Tissue content of high energy phosphates was determined from transmural biopsy after 4 h and 1 week. Infarct size was measured by planimetry of dye-stained heart slices. In the superoxide dismutase and placebo-treated groups, respectively, the mortality rate was 25% and 16%, collateral flow 20 +/- 10 and 23 +/- 18 ml/min per 100 g, area at risk 25 +/- 6% and 26 +/- 7% of the left ventricle and infarct size 28 +/- 19% and 36 +/- 27% of the area at risk. Multiple regression analysis failed to show any beneficial effect of superoxide dismutase treatment on infarct size. Left ventricular ejection fraction, regional segmental shortening of the postischemic area and tissue content of high energy phosphates recovered to a similar extent and at a similar rate in both treated and placebo groups up to 1 week after reperfusion. Thus, in this model of coronary occlusion and reperfusion superoxide dismutase treatment is of no benefit.

Effect of short atrioventricular delay on cardiac output.

Short atrioventricular (AV) delay modifies late diastolic filling dynamics. The effect of this change on cardiac output (CO) was studied in closed chest, AV blocked canine preparations (N:10), during AV sequential pacing (80 bpm). CO (thermodilution technique) and transmitral flow velocity (TMFV, pulsed-wave Doppler) were measured and compared (paired t-test) on the basis of TMFV pattern, when atrial contraction (A wave) started just after early diastolic transmitral flow deceleration (PR: 219 +/- 25 ms, mean +/- SD) and when A wave occurred at the end of late diastole and shortened due to the next ventricular contraction (PR: 56 +/- 11 ms). The short AV delay resulted in 12.0 +/- 5.9% decrease of CO, reflecting the interrupted late diastolic atrial transport. Properly timed atrial contraction is necessary for optimal AV sequential pacing.

Laser apexcardiogram in healthy young men: a comparative study with the conventional method.

Laser displacement technique is a new method to registrate the low frequency precordial movements. In 16 young healthy men the apexcardiograms were obtained subsequently by conventional way and by laser displacement technique. The basic differences in time intervals and amplitude relations were analyzed with paired t-test. On the laser apexcardiogram the peak of the positive deflection generated by ventricular systole came later (p less than 0.001), the proportion of the positive deflection to the total deflection was smaller (p less than 0.01) and the positive deflection elicited by atrial contraction was proportionally larger (p less than 0.05) than on the conventional apexcardiogram. The timing of the onset of systolic positive deflection and of the nadir of diastolic negative deflection were similar in both apexcardiograms. The observed differences are the consequences of the different physical basis of the two methods. The laser apexcardiogram seems to be more sensitive on the diastolic events and permits a better analysis of diastolic phenomena of the curve, including the atrial contraction.

Prevention of pulmonary complications during neonatal resuscitation.

The pulmonary functions were measured during resuscitation of eight critically ill newborns by the "Pulmonary Evaluation and Diagnostic System" (PEDS UNIT-M.A.S. Inc.) The asphyxiated infants (Apgar score 0-3; PH 6, 9) required more aggressive ventilator support than "traditional" cases. The danger of the pulmonary injuries was larger in this period. In spite of this, there were no signs of air leaks syndrome and the oxygenation was improved in every case. Worsening or improving the pulmonary mechanics it is possible to change the ventilator settings immediately. This method seems to be advisable to introduce in the everyday routine to prevent iatrogenic pulmonary complications in such critical situation--the reanimation.

[Continuous respiratory therapy of newborn and premature infants with respiratory disorders]. / Légzészavarban szenvedö újszülöttek és koraszülöttek tartós respirációs kezelése.

2216 newborns and prematures with respiratory distress of different underlying diseases were treated with long term respiratory therapy from 1. Jan. 1975 to 31. Dec. 1985. One part of the patients were born in our hospital, the other part of them were transported from outside. The rate of prematures was 81.2%. The respiratory therapy was applied in 1813 cases because of pulmonary diseases (group 1.), while in 403 cases the respiratory troubles were extrapulmonary in origin (group 2.). The diseases in the first group were as follows: hyaline membrane disease in 482 cases (27.30%), intrauterine pneumonia in 634 cases (34.64%), postnatal pneumonia in 291 cases (15.90%), meconium aspiration syndrome in 110 cases (6.01%), severe RDS-II in 158 cases (8.63%), pulmonary immaturity in 116 cases (6.35%), persistent fetal circulation in 21 cases (1.15%) and pulmonary aplasia on the left in 1 case (0.021%). In the second group the greatest part of the cases were treated for neurological disturbances. We discuss the indications of different types of respiratory therapy and the complications as well. The survival rate was in the first group 59.3%, while in the second only 16.9%. Therefore the respiratory therapy seems to be more effective in the pulmonary diseases of the newborns. The mortality rate and the rate of severe complications were lower among inborn babies because of the early application of the respiratory therapy.