Citations

The major parts of the atrioventricular conduction system of the human heart were traced in 21 instances of ventricular septal defect: 19 were examples of variously located uncomplicated ventricular septal defects and two of the tetralogy of Fallot. In the presence of a ventricular septal defect, the conduction system was found to have a normal course, except when the ventricular septal defect lay in a position normally occupied by the conduction system. In each specimen with a defect posterior and inferior to the crista supraventricularis, the conduction system occupied a position posterior and inferior to the defect. In no instance did the conduction system occupy a position superior to a defect of this type. Defects located in the posterobasal portion of the muscular part of the ventricular septum sometimes were posterior to the main parts of the conduction system, so that the conduction tissue was related to the anterior edge of the defect. No example of a defect lying superior to the crista supraventricularis was studied. In our two examples of tetralogy of Fallot, the position of the conduction system was essentially similar to that occurring in the usual variety of ventricular septal defect, that is, posterior and inferior to the crista supraventricularis.

Physiologic studies have been carried out during the first 3 days after intracardiac repair of tetralogy of Fallot. All patients survived. The ratio between systolic pressure in right ventricle and a systemic artery was 0.7 or less in all cases and did not vary significantly during the period of study. Residual left-to-right shunts of moderate degree were demonstrated in three patients (repaired with Teflon prostheses). In one of these three, no definite evidence of shunt could be found 2 weeks after operation. Additional abnormal circulatory pathways exist in these patients. Clear evidence was obtained of left-to-right shunting through aorticopulmonary collateral connections in one case. Systemic index was usually below normal or in the low normal range. It was usually lower on the second and third postoperative days than on the first postoperative day. Left atrial pressure was sometimes strikingly higher than right atrial pressure 30 minutes after repair, but not thereafter. Pulmonary vascular resistance was normal or slightly elevated. Gas exchange and management were adequate to maintain normal or near normal oxygen and carbon dioxide levels in arterial blood. Mild metabolic acidosis existed on the first 2 days, but had generally cleared by the third day. The implications of these data are discussed relative to ventricular function and performance, adequacy and technic of surgical repair, administration of blood after operation, and the state of preparedness in the lung and left ventricle in patients with tetralogy of Fallot.

Recently we have studied the role of surgical treatment of patients having occlusive cerebrovascular disease, particularly incipient stroke (or focal intermittent cerebrovascular insufficiency). This report concerns 35 pa-patients with incipient stroke in whom circulation was restored to normal by operation on an artery in an attempt to prevent transient ischemic episodes and cerebral infarction. Since all of the patients were neurologically normal at the time of the surgical procedure, we were concerned primarily with the risk of [see tablein the PDF file] the procedure, particularly in terms of cerebral infarction. The operative mortality rate was 8.5 per cent (three patients). Six patients (17 per cent) sustained cerebral infarcts. Four of these had mild neurologic deficits, usually consisting of clumsiness and mildly reduced discriminatory sensation in one hand; one had a severe neurologic deficit, and one died. Evidence shows that at least some of these infarcts resulted from emboli arising from the operative site at the time of or shortly after the operation. The results of long-term follow-up revealed that 66 per cent of the surgically treated patients were normal compared to 25 per cent of a contrast group; and 17 per cent of the treated patients had suffered cerebral infarcts compared to 40 per cent of the contrast group. The long-term results are thus similar to the immediate postoperative results. These findings simply indicate that an operated patient's prognosis was good over the long term if the cerebral ischemic episodes were relieved and if he sustained no complications from the surgical procedure.

The artificial pacemaker has been compared to a physiologic ventricular parasystolic focus. In hearts being driven by a pacemaker, in the absence of atrioventricular (AV) block, capture (interference) phenomena are constantly seen. While variations in QRS complexes have been observed when the external pacemaker stimulus occurs early in the T-wave period of a sinus conducted beat, no sequence of aberrant beats has been observed. One patient showed occasional sinus beats interpolated between ventricular beats arising from the artificial pacemaker, and these occurred at a very narrow time band suggesting that AV conduction was permitted by phenomenon of a supernormal phase. At a later date this patient showed also retrograde conduction believed related to a supernormal phase during recovery of junctional tissue penetrated by an impulse entering from above, though the impulse itself was blocked. Records of two patients are used to illustrate grossly aberrant QRS complexes produced by the stimulus of the electric pacemaker when this fell in the semirefractory period. Noteworthy was the presence of a latent period before potentials of the propagated impulse were recorded, there being evident stimulus-to-QRS delays. The situation wherein the rhythm is most chaotic is that where AV block is absent, the sinus rate is fast, and the electric pacemaker rate is relatively slow. In two patients, retrograde activation of the atria occurred as a stable mechanism. In one patient, nodal rhythm of the RP type occurred, and sequences of the records suggested that the AV node might have become synchronized with the extrinsic pacemaker cycle. In this last instance three independent centers of effective impulse formation coexisted, the sinus node, AV node, and stimulating electrodes of the electronic pacemaker. A marked increase in the refractory period of the ventricle, as measured by its response to the set stimulus of the electric pacemaker delivered at varying instants with respect to the sinus mechanism, occurred in one case within a few days. The possibility that reserpine therapy contributed to this change is possible but has not been established, for the effective refractory period, as measured, later remained constant over a period of many weeks.

Nineteen patients with ventricular septal defect and severe aortic valvular incompetence have been operated on at the Mayo Clinic. There were two early deaths and two late deaths. The ventricular septal defect was located high and anteriorly in the septum and was often small. Aortic valvular incompetence was due, in most cases, to a deformed, prolapsing right coronary cusp. Mild to moderate degrees of infundibular pulmonary stenosis coexisted in nine patients. Repair of the ventricular septal defect was readily accomplished in most cases by direct suture, and relief of obstruction to right ventricular outflow was effected, when required, by resection of the crista supraventricularis. Repair of the aortic incompetence was attempted by a variety of means, but the incidence of persistent significant regurgitation was high, except when prosthetic cusp replacement was used. It is currently our policy to defer operation in children unless there are significant symptoms. When the patient is past the age of about 12 to 14 years, operation is advised under proper circumstances, and it consists generally of suturing of the ventricular septal defect and replacement of the right coronary cusp of the aortic valve.