Maurice Lev

Closed chest catheter desiccation of the atrioventricular junction using radiofrequency energy—A new method of catheter ablation

Closed chest catheter ablation of the atrioventricular (AV) junction has been performed with direct current or laser energy. The effect of 750 kHz radiofrequency energy on ablation of the AV junction was evaluated in 13 dogs. The radiofrequency energy was generated from an electrosurgical generator in the bipolar mode. The radiofrequency output was delivered between two distal electrodes (bipolar ablation) in eight dogs, and between the distal electrode and an external patch electrode (unipolar ablation) in another five dogs at varying power (watts) but with a constant pulse duration of 10 seconds. Complete AV block was achieved in 11 dogs and second degree AV block in 2. During the 4 to 7 day follow-up period, complete AV block persisted in 9 of the 11 dogs with initial complete heart block. The other two had return of AV conduction; one had persistent 2:1 AV block and the other had persistent first degree AV block. Of the two dogs with initial second degree AV block, one developed complete AV block, the other had resumption of 1:1 AV conduction with a normal PR interval. Energy was delivered in 1 to 13 applications per dog. One hundred to 700 J per application was delivered with bipolar ablation and 10 to 100 J with unipolar ablation. There was no damage to the catheter unless the catheter was repeatedly used in excess of 1,500 J of total energy. Ventricular arrhythmias were not observed. Pathologic examination showed well delineated coagulation necrosis at the AV junction without surrounding hemorrhage or mural thrombus. Microscopic findings consisted of necrosis with cell infiltration in the periphery of necrosis. Most injuries involved the AV node, the approaches to the AV node and the penetrating bundle. In conclusion, catheter ablation of the AV junction with radiofrequency energy is safe. It can effectively induce discrete areas of necrosis and produce various degrees of AV block. In addition, ablation by radiofrequency energy has distinct advantages as compared with catheter ablation with direct current or laser energy.

Tachycardia-bradycardia syndrome (so-called “sick sinus syndrome”): Pathology, mechanisms and treatment☆

Abstract The tachycardia-bradycardia syndrome consists of paroxysmal atrial fibrillation, flutter or tachycardia followed by sinoatrial block or sinus arrest resulting in Stokes-Adams attacks. Detailed histologie findings of the conduction system of 2 patients with this entity correlated well with the clinical observation of cardiac rhythm disturbances in the sinus node, atria and atrioventricular (A-V) junction. Eight other patients with the syndrome were studied clinically. The mechanisms (as revealed by the electrocardiogram) producing the bradycardia phase include depression of pacemaker function (arrest) or of conduction (exit block) of the sinus impulse, or both, plus depression of A-V junctional impulse formation. Proper therapy usually requires electrical pacing in conjunction with administration of digitalis or propranolol, or both. Our findings suggest that the term “sick sinus syndrome” is an inaccurate and inappropriate synonym for the tachycardia-bradycardia syndrome.

The pathologic anatomy of mixed levocardia: A review of thirteen cases of atrial or ventricular inversion with or without corrected transposition∗☆

Abstract 1. 1. The pathologic anatomy of thirteen hearts with mixed levocardia was studied. 2. 2. The nomenclature in mixed levocardia of chambers, valves and coronary arteries is discussed. Atria and valves should be designated according to morphology and position. Ventricles should be designated according to their distal connections, in addition. Coronary arteries should be designated left- and right-sided. 3. 3. The cases of mixed levocardia presented and those reviewed in the literature may be divided into type I, with ventricular inversion; type IA, with complete inverted transposition; type IB, with complete (noninverted) transposition; type II with atrial inversion; and type III, with relatively normally situated but wrongly connected chambers. 4. 4. Type IA hearts have certain common external and internal morphologic characteristics and are associated with a spectrum of complexes consisting of combinations of left A-V valve abnormality—insufficiency, stenosis, or Ebsteins malformation; with ventricular septal defect, pulmonary stenosis or atresia, and coarctation of the aorta. 5. 5. Types IB and III are rare. 6. 6. Type II is one of the types of isolated levocardia with or without splenic abnormalities.

Mid-ventricular obstruction: a variant of obstructive cardiomyopathy.

In two patients with clinical and catheterization findings of hypertrophic obstructive cardiomyopathy, the level of intraventricular obstruction was found to be in the mid-ventricular area rather than at the junction of the inflow and outflow tracts. One patient died suddenly shortly after unsuccessful outflow tract myectomy. In vivo recognition of this probably rare variant form of obstructive cardiomyopathy rests mainly on the angiograhic appearance of the left ventricle and on the recording of pressures in multiple sites of the left ventricular cavity. Surgical relief of the obstruction in these patients is not likely to be obtained by a transaortic left ventricular outflow myectomy but may require either papillary muscle resection by the transatrial or transventricular approach or mid-ventricular septectomy, or both.

Single (Primitive) Ventricle

Single ventricle is that condition in which both atrioventricular (A-V) orifices enter a common ventricular sinus, from which the arterial trunks emerge with their coni. The following types of single ventricle were found: (1) with regular (noninverted) transposition in levocardia; (2) with inverted transposition in levocardia; (3) with normal position of arterial trunks in levocardia; (4) in dextrocardia, and (5) in mesocardia. This entity is differentiated from common ventricle which is basically a heart with a large ventricular septal defect. Single ventricle does not include mitral and tricuspid atresia by definition, nor does it include straddling tricuspid orifice, in which two distinct ventricles are present. The concept of single ventricle herein defined differs from de la Cruz and Millers concept of double-inlet left ventricle which includes straddling tricuspid orifice. Embryologically in single ventricle we are dealing with persistence of the primitive state of the bulboventricular loop, due to a lack of expansion of the atrial canal to the right during the process of absorption of the bulbus.

The Dissection of the Atrioventricular Node Bundle and Bundle Branches in the Human Heart

The A-V node, bundle and bundle branches were grossly dissected in 41 human hearts. The method for this dissection is described. Given also are the sizes of the individual structures with advancing age. These structures grow more slowly than the remainder of the myocardium.

The spectrum of common atrioventricular orifice (canal)

Abstract A study was made of the incidence of CAVO, as it occurs by itself and as it is associated with other complexes, and the association of these complexes with Downs syndrome, and splenic abnormalities. It was found that the complete complicated type (associated with other abnormalities) is more common than the complete simple type where there are no splenic abnormalities. All types, complete and incomplete, had balanced, dominant right and dominant left forms, which is important surgically. The simple type, in situs solitus, does not show severe abnormalities of the spleen, but the complicated type does. Incomplete types are rarely associated with severe abnormalities of the spleen. The complete complicated type without splenic abnormalities is less often associated with Downs syndrome than is the complete simple, and the incomplete less often than the complete type. There is an inverse relationship between Downs syndrome and CAVO associated with splenic abnormalities. The association of patent ductus arteriosus with CAVO is favorable, and the association with fetal coarctation or splenic abnormalities is unfavorable for longevity.

Transient and Persistent Atrial Standstill with His Bundle Lesions Electrophysiologic and Pathologic Correlations

Electrophysiologic studies, including His bundle recording and atrial pacing (AP), were performed in one patient with transient (TAS) and another with persistent atrial standstill (PAS). Both subsequently expired, and postmortem examinations with serial sections of the conduction system were obtained. The patient with TAS had left bundle-branch (LBB) block, a P-H interval of 140 msec (normal, 80-140 msec), an H-Q of 40 msec (normal, 35-55 msec), and an AP threshold of 1.2 ma. Postmortem examination revealed total left circumflex occlusion proximal to the sinoatrial (SA) nodal artery takeoff, SA nodal arteriolosclerosis without infarction, and left-sided cardiac skeletal sclerosis (LSCSS) disrupting the penetrating portion of the His bundle and the LBB. Intracardiac recordings in the patient with PAS showed absent atrial activity and an H-Q of 60 msec. The atria were inexcitable with AP up to 15 ma at multiple sites. Postmortem examination revealed a previously undescribed atrial disease characterized by arteriolosclerosis, fibroelastosis, fatty infiltration, and vacuolar degeneration of muscle cells, with only moderate SA and A-V nodal involvement. LSCSS was present, disrupting the branching portion of the His bundle. Thus, TAS reflected SA nodal ischemia without infarction; PAS reflected a new atrial degenerative disease; H-Q was normal with a lesion in the penetrating portion of the His bundle and was prolonged with a similar lesion in the branching portion.

Anatomic Findings in a Case of Ventricular Pre-Excitation (WPW) Terminating in Complete Atrioventricular Block

1. Electrocardiographic and detailed histological studies are presented of a case of ventricular pre-excitation with progressive A-V and intraventricular block terminating in complete A-V dissociation.2. Whereas the demonstration of a tract which leads from the atrial septal musculature to the A-V bundle bypassing the A-V node explains the short P-R interval, the delta wave is accounted for by the demonstration of unusually copious Mahaim fibers from the A-V bundle to the posterior portion of the muscular ventricular septum.3. Thus, this appears to be the first demonstration of Mahaim fibers responsible for A-V transmission in the pre-excitation syndrome.4. The correlation of the data permitted reconstruction of anatomic changes preceding, and responsible for, the gradual progression of the atrioventricular and intraventricular conduction disorder.5. On the basis of this correlation it would appear that the two characteristic criteria of ventricular pre-excitation, shortened P-R and the delta wave, may in some cases have a different anatomic background. A separation of these parameters permits an explanation of certain atypical and puzzling aspects encountered in the syndrome of ventricular pre-excitation and related conditions.

Premature narrowing or closure of the foramen ovale

P remature narrowing or closure of the foramen ovale is an infrequent but not rare anomaly. We have found 25 cases reported in the literature, the details of which are presented in Table I.1-21 Analysis of 1,150 cases of congenital heart disease studied at the Congenital Heart Disease Research and Training Center revealed 10 examples of this anomaly. This is a report of the pathologic anatomy in these 10 cases as studied quantitatively by a method previously reported.22 In addition, this is a clinical-pathologic study of one case in which the diagnosis was strongly suspected clinically.