Surgical management of ventricular tachycardia in subannular left ventricular aneurysm.

Submitral left ventricular aneurysms typically affect young adults of African ancestry. These aneurysms are characterized by heart failure and mitral insufficiency, and occur in the absence of coronary disease. We report a rare case of symptomatic ventricular tachycardia in association with submitral left ventricular aneurysm (and no mitral insufficiency). Ventricular tachycardia was abolished by aneurysm resection and ventricular reconstruction. We suggest surgical management is indicated for ventricular tachycardia associated with this unusual condition, and may be curative.

The effect of external cardiac pacing on stroke volume.

To evaluate the hemodynamic effects of external cardiac pacing, ten subjects with normal left ventricular function were paced at rates approximating their resting heart rates using an external pacemaker while continuous-wave Doppler measurements from the aortic outflow were recorded. The Doppler flow velocity integral was used as an index of stroke volume and the product of heart rate and flow velocity integral was used as an index of cardiac output. At a pacing rate 13% faster (range -5% to 32%) than the rate during sinus rhythm, the mean index of stroke volume was reduced 24% from 17.7 cm to 13.5 cm (P less than 0.0002). However, the faster rate during external pacing partially compensated for the reduced stroke volume resulting in an index of cardiac output that was 14% lower compared to the prepaced index (1,297 vs 1,121 cm [P less than 0.02]). Thus, in subjects with normal LV function, external pacing results in a small drop in cardiac output that may be partially overcome by increasing the pacing rate.

Haemodynamic effects of Ro 13-6438, a new inotropic agent with vasodilating properties.

The chemical class 1,5 dihydroimidazo (2,1-6) guinazolin-2(3H)ones has been shown to have positive inotropic activity, some of its members displaying a favourable ratio between positive inotropic and chronotropic activity. This study was designed to determine the cardiovascular properties of Ro 13-6483, a non-glycoside, non-catechol positive inotropic agent, in anaesthetized, open chest mongrel dogs. Ro 13-6483 (1 mg/kg) was administered intravenously over a 5-min period to 6 dogs. Haemodynamic changes were measured continuously over a period of 45 min. Ro 13-6438 increased stroke volume by 61.9% (p less than 0.001) and cardiac output by 53.3% (p less than 0.001). Systolic and diastolic blood pressure decreased significantly (p less than 0.01). Heart rate did not change. The lowering of the blood pressure, without a significant increase in heart rate, observed after Ro 13-6483 administration might prove to be of value in patients with congestive heart failure, since Ro 13-6483 would reduce afterload and improve the competency of the heart, in addition to the positive inotropic effects.

Pharmacokinetic differences between peripheral and central drug administration during cardiopulmonary resuscitation.

Advanced resuscitation techniques are dependent on drug therapy to increase survival. Because drugs must reach their site of action instantaneously, the choice of appropriate route of administration may be critical. To study the pharmacokinetics of drug administration by peripheral and central venous routes during resuscitation, nine mongrel dogs were studied. Arterial blood pressure and electrocardiograms were monitored continuously. Cardiac output was evaluated before resuscitation to determine control levels. After thoracotomy and fibrillation of the heart, cardiac massage was started with a frequency of compression maintained at 60/min. Bolus injections of two different radioisotopes were given simultaneously through a peripheral and a central vein. Isotope activity was sampled through a catheter in the right femoral artery at 5 second intervals for 90 seconds and at 30 second intervals for 210 seconds. The major differences between the two routes of administration were that central injection produced a 270% higher peak concentration (p less than 0.001) and significantly shorter lag times to the first appearance of tracer (16 +/- 7 versus 38 +/- 13 seconds, p less than 0.05) and times to peak concentration (13 +/- 5 versus 27 +/- 12 seconds, p less than 0.01). In contrast, there were no significant differences in area under the time-counts curve, mean residence time, total body clearance and steady state volume of distribution. The central compartment volume of distribution was significantly smaller after central than after peripheral injection (26.1 +/- 56 versus 76.3 +/- 16.5 ml, p less than 0.01). The therapeutic implications of these findings must be investigated for individual drugs used during cardiorespiratory resuscitation to determine the most appropriate route and dosage for each agent.