Crossed atrioventricular connection with straddling of the right atrioventricular valve

We describe one patient with crossed atrioventricular connection in situs inversus, concordant atrioventricular connection, double outlet right ventricle, and straddling of the right atrioventricular valve. Angiographic features are analyzed, pointing out the importance of selective angiography in order to define the atrioventricular and ventriculoarterial connections. The utility of bidimensional echocardiographic study before cardiac catheterization is emphasized in order to know the associated malformations.     

Crossed atrioventricular connections

Four cases of crossed atrioventricular connections are described. All of them were diagnosed at cardiac catheterization by angiocardiography and one was examined pathologically. Two possessed situs solitus, one with concordant connections and the other with discordant connections; the other had two situs inversus, both of them with concordant connections. Two had double-outlet right ventricle, one had transposition of the great arteries, and the other had normally related and connected great arteries. These cases have been interpreted as representing abnormal rotation of the ventricles following sepatation. A review of 36 cases previously reported on and our own cases, suggests that most patients have concordant atrioventricular connections. There are many types of ventriculo-arterial connections, the most frequent being transposition of the great arteries. There has not been any case reported with persistent truncus arteriosus. On the basis of atrioventriculo-arterial connections, we propose a classification for this malformation. We discuss the importance of the bulboventricular loop in the type of atrioventricular connections, some clinical implications for the diagnosis, and analyze the value of the rules to localize the ventricles by means of the position of the great arteries.     

Atresia of the right atrioventricular orifice with atrioventricular concordance.

Three hearts are described in which a fibrous membrane was interposed between the right atrium and a formed but hypoplastic right ventricle, which possessed recognisable inlet, trabecular, and infundibular components. In these hearts the distribution of the conducting tissue was as expected for concordant atrioventricular connections, and contrasts with that seen in the classical type of ''tricuspid atresia''. The distinctive morphological and histological features of these specimens lend further support to our view that the majority of cases of atresia of the right atrioventricular orifice should be regarded as coming within the designation of ''the univentricular heart''.     

First-degree atrioventricular block

Marked first-degree AV block (PR≥0.30 s) can produce a clinical condition similar to that of the pacemaker syndrome. Clinical evaluation often requires a treadmill stress test because patients are more likely to become symptomatic with mild or moderate exercise when the PR interval cannot adapt appropriately. Uncontrolled studies have shown that many such symptomatic patients with normal left ventricular (LV) function improve with conventional dual chamber pacing (Class IIa indication). In contrast, marked first-degree AV block with LV systolic dysfunction and heart failure is still a Class IIb indication, a recommendation that is now questionable because a conventional DDD(R) pacemaker would be committed to right ventricular pacing (and its attendant risks) virtually 100% of the time. It would seem prudent at this juncture to consider a biventricular DDD device in this situation. Patients with suboptimally programmed pacemakers may develop functional atrial undersensing because the P wave tends to migrate easily into the postventricular atrial refractory period (PVARP). Retrograde vetriculoatrial conduction block is uncommon in marked first-degree AV block so a relatively short PVARP can often be used at rest with little risk of endless loop tachycardia. The usefulness of a short PVARP may be negated by special PVARP functions in some pulse generators designed to time out a long PVARP at rest and a gradually shorter one with activity. First-degree AV block during cardiac resynchronization therapy (CRT) predisposes to loss of ventricular resynchronization during biventricular pacing because it favors the initiation of electrical “desynchronization” especially in association with a relatively fast atrial rate and a relatively slow programmed upper rate. Patients with first-degree AV block have a poorer outcome with CRT than patients with a normal PR interval, a response that may involve several mechanisms. (1) The long PR interval may be a marker of more advanced heart disease. (2) Patients with first-degree AV block may experience more episodes of undetected “electrical desynchronization”. (3) “Concealed resynchronization” whereupon ventricular activation in patients with a normal PR interval may result from fusion of electrical wavefronts coming from the right bundle branch and the impulse from the LV electrode. The resultant hemodynamic response may be superior because the detrimental effects of right ventricular stimulation (required in the setting of a longer PR interval) are avoided.     

迷走性房室阻滞

房室阻滞是指窦房结的电激动从心房传导到心室的过程中,经过房室交界区时传导时间延长,或是窦房结的电激动部分或全部被阻断而不能下传至心室的心电现象,它可以呈持续性,也可以是一过性、反复的间歇性出现。临床上按照病因分为器质性和功能性房室阻滞,