The anatomic substrate for the sick sinus syndrome in adolescence

Two cases are described, one of cardiac sarcoidosis and another of primary cardiac amyloidosis, in which correlation was made between electrophysiologic and postmortem conduction system studies. In Case 1 the electrocardiogram revealed right bundle branch block with first degree and intermittent third degree atrioventricular (A-V) block and recurrent unifocal paroxysmal ventricular tachycardia. Electrophysiologic studies disclosed normal sinus rhythm with prolonged A-H (175 ms) and H-V (60 ms) intervals and extrastimulus induction of repetitive ventricular firing. Postmortem examination revealed a sarcoid aneurysm of the posterior left ventricle and granulomatous infiltration of the A-V node, His bundle and bundle branches. In Case 2 the electrocardiogram revealed sinus bradycardia, a prolonged S-T interval and recurrent ventricular fibrillation. Electrophysiologic studies demonstrated a prolonged sinus nodal recovery time (6,080 ms) and H-V (85 ms) interval. Postmortem examination revealed marked amyloid infiltration of the sinoatrial node, atria, proximal bundle branches and left and right ventricular myocardium.There was thus excellent correlation between electrophysiologic and pathologic findings. These cases indicate the importance of making a clinical diagnosis of the disease that might in some cases allow specific therapeutic intervention in addition to antiarrhythmic therapy.     

Sequelae of atriotomy and ventriculotomy on the endocardium,conduction system and coronary arteries

The endocardium was analyzed in all four chambers of 99 hearts with various types of congenital heart defects in which surgical repair was performed more than 6 weeks before death. The findings were compared with those of normal hearts in similar age groups. In some cases the endocardium was microscopically examined. This study revealed that in many cases all four chambers had fibroelastosis of the endocardium (diffuse regardless of the type of surgery done previously). These data suggest that diffuse fibroelastosis can occur as a result of surgical intervention and may be related to blocked lymphatic drainage. Sudden death in some patients long after surgery for congenital heart disease and the failure of the chambers to regress to normal size in some cases after total surgical repair may be related to fibroelastosis of the chambers.The sinoatrial node may be injured in atriotomy and in the performance of the Mustard procedure. Ventriculotomy may injure the right bundle branch. Ventriculotomy may also injure the coronary supply to the right ventricle or rarely the anterior descending coronary artery.     

Lack of connection between the atria and the peripheral conduction system in a case of corrected transposition with congenital atrioventricular block

This is the first documented histologic study of the heart of a patient with corrected transposition of the great vessels and congenital atrioventricular (A–V) block with no connection between the atria and an anterior type of peripheral conduction system. Musculature in the superior (anterior) walls of both atria was absent, as was the anterior A–V node. The peripheral conduction system began with the bundle of His. In place of the absent atrial musculature, fibrosis and calcification were present. The relation of laboratory evidence of connective tissue dyscrasia in the mother to the congenital A–V block in the child is discussed.     

Mahaim and James fibers as a basis for a unique variety of ventricular preexcitation

This report concerns pathologic findings in a 54 year old woman with intermittent preexcitation who died of carcinoma of the breast. Electrocardiograms revealed predominantly normal sinus rhythm with a normal P-R interval and narrow QRS complex. Episodes of sinus rhythm, short P-R interval and QRS widening (with delta wave) were also recorded. During preexcitation QS complexes were noted in leads II, III, aVF, V₁ and V₄ to V₆. Delta waves were negative in leads II, III, aVF and V₁, isoelectric in leads V₄ to V₆ and positive only in leads I, aVL, V₂ and V₃. This case thus defies classification into any known variety of preexcitation.

Complete serial sections, cut through the entire conduction system and both atrioventricular (A-V) rims, totaled 18,600 sections. These revealed no bundle of Kent. Instead, Mahaim fibers histologically identified as His bundle tissue gave off from the A-V bundle to both the right and the left sides of the septum associated with the normal fibers of James. This case reveals that (1) fibers of James can bypass the A-V node, (2) fibers of Mahaim can conduct, and (3) there are types of preexcitation in addition to types A and B.     

Pathologic correlations in a case of complete heart block with split his potentials resulting from a stab wound of the heart

A 23 year old previously healthy man was stabbed in the anterior chest. This resulted in a ventricular septal defect and complete atrioventricular (A-V) block. The electrocardiogram revealed complete A-V block with a QRS pattern of right bundle branch block. His bundle recordings 26 days later revealed A-V dissociation with split His potentials (P-H₁ interval of 100 msec and H₂-V interval of 40 msec). During the study the escape QRS shifted from right to left bundle branch block with H₂ potentials still preceding each QRS interval with H₂-V intervals of 40 msec. A permanent pacemaker was implanted because of persistent congestive heart failure and bradycardia due to A-V block. The patient subsequently became asymptomatic. He died suddenly 3 $\text{1}\text{2}$ years later.Pathologically there were sizable openings in both the tricuspid and mitral valve substance and a ventricular septal defect involving the pars membranacea and part of the adjacent muscular septum. Serial sections of the conduction system revealed total destruction and fibrous replacement of the bifurcation and beginning of the right and left bundle branches and subtotal fibrous replacement of the branching bundle. Thus, the bifurcation of the bundle of His was totally absent at autopsy despite apparent electrophysiologic evidence of its existence 26 days after the stab wound. A possible explanation for this discrepancy is the subsequent fibrosis of the bifurcation produced by hemodynamic changes at the lower margin of the ventricular septal defect.     

Conduction system in systemic lupus erythematosus with atrioventricular block

We describe the clinical course and the postmortem cardiac findings in a 12 year old girl with systemic lupus erythematosus, complete heart block, renal failure and hyperkalemia. The conduction system was examined by serial section. The sinoatrial and atrioventricular nodes were found to be almost completely replaced by granulation tissue; we believe that this finding is related to the systemic lupus. The hyperkalemia is not considered to be the cause of the block, since the block persisted despite the lowering of the blood potassium level and the morphologic findings in this case are not found in hyperkalemia.     

Conduction system in a patient with Prinzmetal's angina and transient atrioventricular block.

His bundle recordings obtained during and between attacks of Prinzmetal's variant angina and transient atrioventricular (A-V) block were followed by a comprehensive serial section study of the conduction system in a 33 year old woman. Recordings between attacks showed normal A-H and H-V intervals. During an attack there was block proximal to the His bundle recording site. Pathologic studies revealed severe narrowing of the right coronary artery. Arteriolosclerosis of the heart was diffuse. Insignificant changes were found in the approaches to the A-V node and the A-V node itself. Major changes found in the left bundle branch had no counterpart in the electrocardiogram; the discordance in these findings is discussed.     

Pathologic correlations in three cases of bilateral bundle branch disease with unusual electrophysiologic manifestations in two cases.

Examination of the conduction system in three patients with bifascicular block who had electrophysiologic studies forms the basis for this report. Patients 1 and 2 had left bundle branch block and Patient 3 right bundle branch block and left axis deviation. The H-V interval was prolonged in each case (70, 65 and 60 msec, respectively). Serial section examination of the conduction system revealed sclerodegenerative involvement of both bundle branches in all cases. In Case 1, atrial extrastimulus testing converted left to right bundle branch block; in Case 2, it delineated a sinus echo zone with repetitive sinus nodal reentrance. In the latter case serial section revealed extensive amyloid infiltration of the approaches to the sinoatrial (S-A) node and the atrial preferential pathways. In Case 3, with right bundle branch block and left axis deviation, serial section revealed greater involvement of the anterior part of the main left bundle branch than of the posterior portion as well as involvement of the second part of the right bundle branch. The study revealed excellent correlation between electrophysiologic and pathologic findings in three cases of intraventricular conduction disease and demonstrated an anatomic basis for the electrophysiologic findings resembling alternating bilateral bundle branch block. Sinus nodal reentrance may be related to disease in the approaches to the S-A node thereby causing delay in perinodal tissue allowing sinus reentrance. Finally in Case 3, the anatomic substrate for left axis deviation may lie in a greater involvement of the anterior portion than of the posterior portion of the main left bundle rather than in the corresponding portions of the periphery.     

Quantitative angiographic and morphologic aspects of aortic valve atresia

Quantitative angiographic measurements were performed in 15 infants aged 1 to 35 days who had aortic valve atresia with intact ventricular septum and hypoplastic left ventricle. Thirteen infants had similar measurements performed at autopsy. The latter measurements were smaller than those found at angiography (because of shrinkage), but their relationship was predictable. Angiographic right ventricular (RV) volumes were 2 and 4 times normal in diastole and systole, respectively. The RV volume measured at autopsy was > 3 times normal. Mean RV ejection fraction was 0.40; it was below normal in 10 infants. Maximal right atrial volume was > 2 times normal, and mean left atrial maximal volume was two-thirds normal. The relation between circumferences of the aortic arch and ascending and descending aorta was similar at angiography and autopsy.     

Postmortem digoxin tissue concentration and organ content in infancy and childhood

The concentration of digoxin in tissues and the content of the drug in various organs are reported in 36 infants and children. Sixteen received the drug on a short-term basis and 20 on a long-term basis. The drug was given intravenously to 12, orally to 17, and by intramuscular injection to 7. The study was conducted to determine distribution of digoxin in infants and children and to examine the forensic implications related to digoxin overdosage. Upper therapeutic concentration thresholds for digoxin were established in various tissues. These are different for preterm and full-term neonates than for older children and adults; for example, adult and neonatal values for postmortem blood specimens are 8 and 15 ng/ml, and for ventricular myocardium are 250 and 450 ng/g, respectively. The chronically digitalized premature infant retains in most tissues a considerably larger fraction of digoxin than more mature infants and children. This is in accord with previously demonstrated lower renal digoxin levels in premature infants attributed to their reduced ability to excrete this drug.     

Epicardial activation of the human ventricle: Effects of left ventricular hypertrophy

To determine the effects of left ventricular hypertrophy on eplcardlal activation of the human heart, Intraoperative eplcardlal mapping of 40 to 66 points was performed In 10 patients undergoing aortic valve replacement. Mean calculated left ventricular mass was 364 ± 98 g. All patients had normal left ventricular contraction. Earliest eplcardlal activation occurred In the anterior right ventricle In all patients. In 9 patients, it was the only eplcardlal breakthrough point. One patient had a single Inferior left ventricular breakthrough point. Eplcardlal activation spread from the right ventricle towards the left ventricle in both the anterior and inferior direction. Latest eplcardlal activation occurred at the base of the left ventricle In 9 patients and the base of the right ventricle In 1.When compared with patients with coronary artery disease, normal ventricular contraction, and no left ventricular hypertrophy, patients with hypertrophy had fewer left ventricular breakthrough points (p <0.001) and were more likely to have latest activation at the left ventricular base (p <0.001).We conclude that left ventricular hypertrophy Is associated with marked changes In the pattern of epicardlal activation. These changes may reflect delay In spread from endocardium due to the increased wall thickness.     

Electrophysiologic studies in tricuspid atresia

Five patients with tricuspid atresia underwent His bundle studies with the recording catheter placed close to the mitral valve ring. Right atrial pacing and measurement of the refractory periods were performed in three. The prolonged intraatrial conduction time found in all patients is thought to be caused by a hypertrophied and dilated right atrium with increased internodal distance due to stretching of internodal pathways. The A-H interval was normal in all; the H-V interval was short in three and normal in two. The pattern of left axis deviation in the group with a short H-V interval is thought to be due to early origin of the posterior branches of the left bundle branch from the bundle of His and early activation of the posteroinferior parts of the left ventricle. The pattern of left axis deviation in the group with a normal H-V interval may be related to the previously reported anomalous course of the left bundle. Atrial pacing produced a normal response. The refractory periods were within normal range, suggesting functional integrity of conduction through the atrioventricular node and bundle branches.     

Electrophysiologic effects of ouabain in patients with preexcitation and circus movement tachycardia

Effects of intravenous ouabain were evaluated in 19 patients with an anomalous conduction pathway (14 with manifest and 5 with concealed preexcitation) utilizing intracardiac stimulation and recording. Anterograde conduction through the anomalous pathway was present in all 14 patients with manifest preexcitation at a maximal atrial paced rate of 140 to 250 beats/min (mean ± standard error of the mean 214 ± 7.2) before and at 150 to 240 beats/min (mean 206 ± 7.1) after ouabain (difference not significant [NS]). The anterograde effective refractory period of the anomalous pathway, measured at an equivalent atrial paced rate in 10 patients, was 250 to 450 ms (mean 309 ± 19.7) before and 260 to 450 ms (mean 300 ± 17.2) after ouabain (NS). Retrograde conduction through the anomalous pathway was possible at maximal ventricular paced rates (17 patients) of 160 to 250 beats/min (mean 222 ± 6.6) before and 190 to 250 beats/min (mean 221 ± 4.4) after ouabain (NS). Sustained atrioventricular (A-V) reentrant paroxysmal supraventricular tachycardia was inducible in all 19 patients before and in 17 patients (89 percent) after ouabain (tachycardia could not be induced in two patients because of increased A-V nodal refractoriness). The mean cycle length of tachycardia in the 17 patients was 320 ± 6.7 ms before and 340 ± 8.1 ms after ouabain (p <0.01).In conclusion, ouabain has no significant effect on either anterograde or retrograde anomalous pathway refractoriness. Although ouabain slightly increases the cycle length of tachycardia, it does not interfere with induction of tachycardia in most patients with preexcitation. Oral cardiac glycosides alone would appear to be of limited value in patients with preexcitation and recurrent supraventricular tachycardia.     

Alteration of left ventricular performance by left bundle branch block simulated with atrioventricular sequential pacing

The effects of atrioventricular (AV) sequential pacing-induced left bundle branch block (LBBB) on left ventricular (LV) performance were evaluated during cardiac catheterization in 9 randomly selected patients being investigated for chest pain. All patients were in normal sinus rhythm with a normal P-R interval and QRS duration. LV performance was assessed by both hemodynamic and angiographie measurements. The maximal rate of LV pressure increase (dP/dt), rate of maximal LV pressure decrease ($\text{?dP}\text{dt}$), LV end-diastolic pressure (LVEDP), end-diastolic volume (LVEDV), end-systolic volume (LVESV), stroke volume and percent ejection (EF) were measured during right atrial and AV sequential pacing at a constant pacing rate. The average pacing rate was 97 ± 3 beats/min (mean ± standard error of the mean). In each patient, both dP/dt and $\text{?}\text{dP}\text{dt}$ decreased significantly (p < 0.001) during AV sequential pacing compared with atrial pacing at the same rate, from 1,541 ± 68 to 1,319 ± 56 mm Hg/s for dP/dt and from 1,506 ± 86 to 1,276 ± 92 for $\text{?dP}\text{dt}$. LVEDP did not change significantly when atrial (17 ± 3 mm Hg) and AV sequential pacing (16 ± 2 mm Hg) were compared. Mean LVEDV did not change during atrial (135 ± 13 ml) or AV sequential pacing (137 ± 14 ml). In contrast, the LVESV during AV sequential pacing was higher by 15 ml (23 % ) (from 48 ± 10 to 63 ± 12 ml) (p < 0.001); as a result, the stroke volume was lower by 13 ml (15%) and the EF decreased by 10 %, from 66 to 56 % (?15 %).These changes in LV performance during acutely induced LBBB by AV sequential pacing as compared with atrial pacing at the same rate were independent of altered preload, because both LVEDP and LVEDV were similar during the 2 different pacing modes. Peak systolic pressure during AV sequential pacing was significantly lower than that during atrial pacing (161 ± 10 vs 145 ± 10 mm Hg, p < 0.01), and thus afterload was presumably altered during the different pacing modes. However, because the observed change in systolic pressure (afterload) was lower during AV sequential pacing, this change should improve rather than result in deterioration of ejection phase indexes. Because the opposite was observed, it is concluded the deterioration in LV function noted during AV sequential pacing must be due in part to the asynchronous pattern of ventricular activation induced by this intervention.     

Effects of propranolol on anomalous pathway refractoriness and circus movement tachycardias in patients with preexcitation

Electrophysiologic effects of intravenous propranolol, 0.1 mg/kg, were evaluated in 18 patients with anomalous pathways utilizing intracardiac stimulation and recording. Fourteen patients had Wolff-Parkinson-White syndrome and four had concealed ventricular preexcitation. Anomalous pathway effective refractory period could be measured during the control period and after propranolol administration in nine patients and was 304 ± 7.5 (mean ± standard error of the mean) and 304 ± 8.3 msec, respectively (difference not significant). Ventricular paced 1:1 ventriculoatrial (V-A) conduction (reflecting retrograde anomalous pathway conduction) measured in 12 patients was intact during both the control period and after propranolol at rates of 170 to 200/min. Sustained paroxysmal supraventricular tachycardia was induced in 14 patients during the control period and in 10 after propranolol (in 4 of whom the tachycardia could not be sustained because of atrioventricular [A-V] nodal refractoriness). Mean cycle length of tachycardia in these 10 patients was 328 ± 18 (control) and 352 ± 19 msec (propranolol) (P < 0.01). The increase in tachycardia cycle length reflected an increase in A-V nodal conduction time (A-H interval).In conclusion: (1) Propranolol has an insignificant effect on both anterograde and retrograde anomalous pathway properties. (2) In most cases, propranolol does not interfere with induction of sustained circus movement tachycardia. However, it does produce a statistically significant but slight slowing of the rate of tachycardia. (3) In a minority of cases, propranolol inhibits induction of sustained paroxysmal supraventricular tachycardia by increasing A-V nodal refractoriness.     

Value of the QRS complex in assessing left ventricular ejection fraction

The relation between electrocardiographic findings and the angiographic left ventricular ejection fraction and the augmented ejection fraction after a premature ventricular contraction was investigated in 73 patients with documented chronic coronary artery disease. The patients were separated into four groups according to the presence or absence of abnormal Q waves. Twenty-four patients had diaphragmatic myocardial infarction, 21 had anterior myocardial infarction, 15 had both and 13 had no myocardial infarction. There were no statistically significant differences in cardiac index, left ventricular end-diastolic pressure or number of coronary vessels showing critical narrowing in the four groups. The sum of R waves (in mv) in leads aVL, aVF and V₁ to V₆ (ΣR) was correlated with the ejection fraction (EF) and the augmented ejection fraction (EFa). EF in percent = 6.6 ΣR mv + 9.4 (no. = 73, r = 0.61); and EFa in percent = 8.6 ΣR mv + 11.0 (no. = 73, r = 0.77). Among patients with ΣR of less than 4.0 mv, augmented ejection fraction was less than 0.45 in 73 percent; among patients with ΣR of 4.0 mv or more the augmented ejection fraction was greater than 0.45 in 93 percent (P < 0.001). Thus, the ΣR, calculated from six precordial and two augmented leads in patients with chronic coronary artery disease, correlated with both ejection fraction and augmented ejection fraction. The electrocardiogram in patients with coronary artery disease may prove useful as a simple, readily available and noninvasive guide in the assessment of left ventricular function in patients with coronary artery disease.     

Occlusive disease confined to the right coronary artery: Clinical features, surgical treatment and long-term follow-up in 124 patients

The clinical presentation and surgical results in 124 consecutive patients who underwent aorta to right coronary arterial bypass surgery from January 1970 through June 1977 were reviewed. Preoperatively, 75 percent of the patients were in New York Heart Association functional class III or IV, 9 percent presented with unstable angina and 5 percent had life-threatening ventricular arrhythmias. All patients had high grade occlusive disease confined to the right coronary artery; 34 percent of the patients had associated nonsignificant disease (less than 50 percent intraluminal narrowing) of the left anterior descending or circumflex artery. Left ventricular function was normal in 63 percent and minimally impaired in 37 percent. The operative mortality rate was 1.6 percent. The course of the 122 survivors was followed up for 3.7 years. There were four late deaths, and the 5 year mortality rate was 4.0 percent. Eight patients were reoperated on because of recurrence of symptoms and occlusion of the graft or progression of occlusive disease of the other major coronary arteries, or both. Of the remaining 110 patients, 98 are either in functional class I or II, 60 are taking no cardiovascular medications, 52 are working full time without angina and 73 are asymptomatic. In summary, bypass surgery for isolated right coronary artery disease has a low mortality rate and results in excellent long-term symptomatic improvement.     

Echocardiographic evidence for early left ventricular hypertrophy in dogs with renal hypertension

To investigate the rate of development of left ventricular hypertrophy, left ventricular wall thickness was measured with M mode echocardiography in 12 unanesthetized dogs for several weeks before and for 8 weeks after the induction of hypertension. Hypertension was produced by wrapping one kidney in silk and performing contralateral nephrectomy 2 weeks later. Echocardiographic measurements were performed two to three times weekly and were averaged. The intraobserver and Interobserver variability of left ventricular posterior wall thickness measurements was, respectively, 3.9 percent (correlation coefficient [r] = 0.96, n = 27) and 5.4 percent (r = 0.93, n = 14). Left ventricular wall thickness during the baseline period was 7.8 ± 0.2 mm (mean ± standard deviation) with a coefficient of variation of 2.9 percent. After the wrapping of one kidney in silk, the mean arterial pressure increased by 10 mm Hg during week 1 (difference not significant) and by 12 mm Hg during week 2 (p < 0.05). After contralateral nephrectomy, mean arterial pressure increased by 46 mm Hg (p < 0.001) in 1 week and remained near that level for the rest of the study. In contrast, a significant increase in left ventricular wall thickness occurred during week 1 after wrapping (p < 0.05). A gradual increase in left ventricular wall thickness continued during the entire study.

Sequential M mode echocardiography in dogs is a sensitive and reproducible method of detecting small changes in left ventricular wall thickness. The early increase in left ventricular wall thickness in hypertensive dogs with only minimal increase in mean arterial pressure and the dissociation between the rate of development of hypertension and of left ventricular hypertrophy suggest that factors other than the pressure overload also may contribute to the initiation and evolution of cardiac hypertrophy.