SUMMARY Twelve patients with evidence of Mahaim fibers are reported, six with nodoventricular (NV) fibers and six with fasciculoventricular (FV) fibers. All patients with NV fibers had left bundle branch block morphology, and a sustained reentrant tachycardia with this morphology was proved in each case. In three of the six, ventriculoatrial dissociation occurred during tachycardia. We postulate that the mechanism of this tachycardia is a macroreentry circuit using the NV fiber for the antegrade limb and the His-Purkinje system with a portion of the atrioventricular node for the retrograde limb. ECGs of patients with FV fibers were varied, suggesting a functional relation to the right or left side of the septum. No direct relationship of FV fibers to observed arrhythmias could be found.THE ROLE of Mahaim fibers in the genesis of cardiac arrhythmias in man has been controversial since they were first described.' The initial report was limited to fibers connecting the His bundle to the septum, but this was soon broadened to include fibers connecting the atrioventricular (AV) Received March 25, 1980; revision accepted November 14, 1980. Circulation 64, No. 1, 1981. All patients were admitted to the hospital and placed on continuous telemetry; all cardioactive medications were discontinued. Before cardiac catheterization, all had history and physical examination, routine blood work, ECG, chest x-ray, and twodimensional echocardiography using a microcavitation technique. All patients gave informed consent before catheterization. Electrophysiologic StudyAll patients were studied in the postabsorptive, nonsedated state using techniques previously described.15' 60, 58, '9 Multiple electrode catheters were used to record and pace from the right atrium, the left atrium via the coronary sinus, and the right ventricle. Observations were made during overdrive pacing and refractory period determination from all three locations, during tachycardia and after deliberate induction of atrial fibrillation. TerminologyRecently, Anderson et al.'5 suggested that there are two main anatomic types of Mahaim fibers -nodoventricular (NV) fibers, which arise from the AV node, and fasciculoventricular (FV) fibers, which arise from the His bundle and bundle branches. Because the functional consequences are significant, we have found it useful to consider the two groups separately according to an anatomic and functional classification ( fig. 1). Anderson et al. proposed two varieties of NV fibers -those which arise from the transitional zone of the AV junction and those which arise from the deep, compact nodal portion of the AV junction. NV fibers, depending on level of takeoff relative to the area of physiologic delay, can be associated with either a short or normal PR interval. Ventricular activation in this case results from fusion of impulse propagation via the NV fiber and the normal conduction system, resulting in QRS complexes with varying degrees of anomalous conduction. The PR interval should be normal with isolated FV fibers...

A retrospective analysis was undertaken to define the natural history and long-term follow-up of a group of patients with Marfan's syndrome. Eighty-four patients were diagnosed between January 1959 and June 1987 as having Marfan's syndrome; 68% were male; their ages ranged from 2 to 67 years (mean 26.6). Sixteen patients constituted the early surgical group (those who underwent surgery before 1979; mean age 36.1 years). Nineteen patients constituted the late surgical group (surgery in 1979 or later; mean age 33.3 years). The nonsurgical group comprised 49 patients (mean age 19.3 years). Fifty-seven percent of the patients had a diastolic murmur and 38% had cardiomegaly at presentation. Fifty-seven percent underwent cardiac catheterization, which revealed aortic root dilation (85%), aortic regurgitation (73%), aortic dissection (33%) and mitral regurgitation (36%). Thirteen of the 19 patients in the late surgical group received a composite graft repair of the ascending aorta as compared with only 2 of the 16 in the early surgical group. Follow-up information was obtained on 81 (96%) of 84 patients; the follow-up time was 2 to 332 months (mean 99). Thirty-one of the 81 patients died at age 3 to 63 years (mean age 35 years); 87% of the known causes of death were related to the cardiovascular system. Sixty-one percent of deaths were the result of aortic dissection or rupture or sudden cardiac death. Of the 50 survivors, 98%, including all patients in the late surgical group, were in functional class I or II. Overall survival at 5, 10 and 15 years after operation was 78.4%, 57.1% and 49.5%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

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The long-term prognosis of adult patients with patent ductus arteriosus treated medically or surgically has not been demonstrated. One hundred seventeen adult patients ranging in age from 18 to 81 years (mean 36) were followed up for 1 to 37 years (mean 18). Forty-five patients were treated nonsurgically and 72 had surgical closure. The nonsurgical group experienced significantly more cyanosis (p = 0.002) and had fewer diastolic murmurs (p greater than 0.001) than did the surgical group. In the nonsurgical group, patients with cardiomegaly before treatment were more likely to die (p greater than 0.001) than were patients who did not have cardiomegaly. In the surgical group, patients with cardiomegaly before treatment had a worse prognosis (p = 0.09) than that of patients with normal heart size. Seven patients, five in the nonsurgical and two in the surgical group, presented with a pulmonary artery systolic pressure greater than 100 mm Hg. Five of these patients are alive and well at a mean follow-up time of 18 years. The two nonsurvivors were in the nonsurgical group and died at 4 and 19 years of follow-up, respectively. Adult patients with patent ductus arteriosus should be treated surgically, especially if cardiomegaly is seen at initial presentation.

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