Virtual Histology of Cortical Thickness and Shared Neurobiology in 6 Psychiatric Disorders

IMPORTANCE

Large-scale neuroimaging studies have revealed group differences in cortical thickness across many psychiatric disorders. The underlying neurobiology behind these differences is not well understood.

OBJECTIVE

To determine neurobiologic correlates of group differences in cortical thickness between cases and controls in 6 disorders: attention-deficit/hyperactivity disorder (ADHD), autism spectrum disorder (ASD), bipolar disorder (BD), major depressive disorder (MDD), obsessive-compulsive disorder (OCD), and schizophrenia.

DESIGN, SETTING, AND PARTICIPANTS

Profiles of group differences in cortical thickness between cases and controls were generated using T1-weighted magnetic resonance images. Similarity between interregional profiles of cell-specific gene expression and those in the group differences in cortical thickness were investigated in each disorder. Next, principal component analysis was used to reveal a shared profile of group difference in thickness across the disorders. Analysis for gene coexpression, clustering, and enrichment for genes associated with these disorders were conducted. Data analysis was conducted between June and December 2019. The analysis included 145 cohorts across 6 psychiatric disorders drawn from the ENIGMA consortium. The numbers of cases and controls in each of the 6 disorders were as follows: ADHD: 1814 and 1602; ASD: 1748 and 1770; BD: 1547 and 3405; MDD: 2658 and 3572; OCD: 2266 and 2007; and schizophrenia: 2688 and 3244.

MAIN OUTCOMES AND MEASURES

Interregional profiles of group difference in cortical thickness between cases and controls.

RESULTS

A total of 12 721 cases and 15 600 controls, ranging from ages 2 to 89 years, were included in this study. Interregional profiles of group differences in cortical thickness for each of the 6 psychiatric disorders were associated with profiles of gene expression specific to pyramidal (CA1) cells, astrocytes (except for BD), and microglia (except for OCD); collectively, gene-expression profiles of the 3 cell types explain between 25% and 54% of variance in interregional profiles of group differences in cortical thickness. Principal component analysis revealed a shared profile of difference in cortical thickness across the 6 disorders (48% variance explained); interregional profile of this principal component 1 was associated with that of the pyramidal-cell gene expression (explaining 56% of interregional variation). Coexpression analyses of these genes revealed 2 clusters: (1) a prenatal cluster enriched with genes involved in neurodevelopmental (axon guidance) processes and (2) a postnatal cluster enriched with genes involved in synaptic activity and plasticity-related processes. These clusters were enriched with genes associated with all 6 psychiatric disorders.

CONCLUSIONS AND RELEVANCE

In this study, shared neurobiologic processes were associated with differences in cortical thickness across multiple psychiatric disorders. These processes implicate a common role of prenatal development and postnatal functioning of the cerebral cortex in these disorders.

Lifestyle factors and reproductive health: taking control of your fertility

Approximately 10 to 15% of couples are impacted by infertility. Recently, the pivotal role that lifestyle factors play in the development of infertility has generated a considerable amount of interest. Lifestyle factors are the modifiable habits and ways of life that can greatly influence overall health and well-being, including fertility. Many lifestyle factors such as the age at which to start a family, nutrition, weight, exercise, psychological stress, environmental and occupational exposures, and others can have substantial effects on fertility; lifestyle factors such as cigarette smoking, illicit drug use, and alcohol and caffeine consumption can negatively influence fertility while others such as preventative care may be beneficial. The present literature review encompasses multiple lifestyle factors and places infertility in context for the couple by focusing on both males and females; it aims to identify the roles that lifestyle factors play in determining reproductive status. The growing interest and amount of research in this field have made it evident that lifestyle factors have a significant impact on fertility.

The influence of patient strength, aerobic capacity and body composition upon outcomes after coronary artery bypass grafting

BACKGROUND

Physical activity, physical fitness and body habitus of patients may be important predictors of outcomes after cardiac surgery. This study sought to quantify physical fitness and determine whether components of fitness enhance the prediction of outcomes in a group of patients undergoing coronary artery bypass grafting.

METHODS

A group of 200 patients were evaluated prior to coronary artery bypass surgery. A Veterans Specific Activity Questionnaire (VSAQ) measured aerobic capacity. A grip dynamometer assessed strength. Skin-fold thickness was used to calculate percent body fat and lean body mass index. Patients were divided into low risk (0-2.5%) and high risk (>2.5%) groups based on the STS National Cardiac Surgery Database prediction of operative mortality.

RESULTS

Patients with both a high percent body fat and a low VSAQ were at higher risk for at least one serious complication (p<0.05) and a longer postoperative length of stay (p<0.05).

CONCLUSION

This study suggests: 1) An index of physical fitness can be obtained preoperatively in cardiac surgical patients; 2) This information aids in the prediction of operative risk.

Effects of combined aerobic and resistance training versus aerobic training alone in cardiac rehabilitation

PURPOSE

This study examined the effects of performing combined resistance and aerobic training, versus aerobic training alone, in patients with coronary artery disease.

METHODS

Thirty-six patients with coronary artery disease were randomized to either an aerobic-only training group (AE) or a combined aerobic and resistance training group (AE + R). Both groups performed 30 minutes of aerobic exercise 3 days/week for 6 months. In addition, AE + R group performed two sets of resistance exercise on seven different Nautilus machines after completion of aerobic training each day. Twenty patients (AE: n = 10; AE + R: n = 10) completed the training protocol with > 70% attendance.

RESULTS

Strength gains for AE + R group were greater than for AE group on six of seven resistance machines (P < 0.05). VO2peak increased after training for both AE and AE + R (P < 0.01) with no difference in improvement between the groups. Resting and submaximal exercise heart rates and rate-pressure product were lower after training in the AE + R group (P < 0.01), but not in the AE group. AE + R increased lean mass in arm, trunk, and total body regions (P < 0.01), while AE increased lean mass in trunk region only (P < 0.01). Percent body fat was reduced for AE + R after training (P < 0.05) with a between group trend toward reduced body fat (P = 0.09). Lean mass gain significantly correlated with strength increase in five of seven resistance exercises for AE + R.

CONCLUSIONS

Resistance training adds to the effects of aerobic training in cardiac rehabilitation patients by improving muscular strength, increasing lean body mass, and reducing body fat.

Mobile cardiac catheterization: comparison with outpatient and inpatient catheterization at tertiary facilities

The study group included 1,553 consecutive patients from areas serviced by our mobile catheterization laboratories: 719 procedures were performed in the mobile unit at their local hospitals, 277 were performed at a tertiary hospital with less than a 24 hr hospital stay, and 557 were performed at a tertiary hospital as inpatients. The indications for mobile catheterization were predominantly atypical chest pain, angina pectoris, or positive treadmill stress test, whereas patients with less than 24 hr hospitalization at the tertiary center had their catheterization performed for additional reasons. The majority of the inpatient indications were for recent myocardial infarction or unstable angina. Using the American College of Cardiology/American Heart Association (ACC/AHA) criteria for outpatient catheterization, the mobile catheterizations were performed safely with a complication rate of only 0.7% compared to a complication rate of 3.1% for inpatients demonstrating that a low risk group of patients can be prospectively identified and catheterized safely in the mobile setting. An extremely high risk group of patients with ongoing unstable angina and recent myocardial infarction was also identified which should undergo catheterization only at a tertiary center.

Mobile cardiac catheterization registry: report of the first 1,001 patients

The purpose of this study was to evaluate prospectively the efficacy and safety of mobile cardiac catheterization. Mobile cardiac catheterization was introduced into clinical practice in 1989, but there has been no systematic study of its performance and safety. A registry was established in 1989 to monitor outcomes with mobile cardiac catheterization and is reported here. Patients were screened for eligibility for mobile cardiac catheterization using the joint AHA/ACC criteria for outpatient angiography. Eligible patients underwent mobile catheterization at eight hospitals within 120 miles of the base tertiary center. Helicopter evacuation services were available at each mobile site. The indications, findings, dispositions, and complications of mobile cardiac catheterization were recorded by means of a checklist, telephone follow-up and chart review. A total of 1,001 consecutive patients were entered into the registry in the first 20 months of operation, including 436 females and 565 males aged 22 to 84 years. Angina (Canadian Classes II-IV) was the most frequent primary indication for catheterization (46.4%), followed by atypical chest pain (36.9%), or a positive exercise stress test (25.6%). Infrequent indications for catheterization included a history of myocardial infarction (5.6%), congestive heart failure (7.1%), arrhythmias (4.1%), and valvular heart disease (0.7%). Catheterization was accomplished in 99.9% of patients. Angiographically normal studies were observed in 22.8%, and mild (< or = 50%) coronary artery disease in 13.6% of patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Intravascular extraction of chronic pacemaker leads: efficacy and follow-up

Extraction of chronic pacemaker leads has been recommended for infections, prevention of venous thrombosis, migration, and possible perforation. Success with constant traction techniques has been variable, and the cost and morbidity of open chest surgical procedures are prohibitive. Efficacy of a new system for lead extraction using intravascular techniques was analyzed. The system (Cook Pacemaker) uses a locking stylet, which is secured at the distal electrode by counterclockwise rotation to reinforce the lead and facilitate traction, and dilator sheaths that are used to free the lead from adhesions in the venous system. In a series of 56 patients (ages 19-88) who presented for lead extraction because of erosion (5), infection (14), lead replacement (35), or other (2), 86 leads were extracted. Thirty-two were atrial leads and 54 ventricular; 23 had active fixation and 63 passive. Average duration of implant was 58 +/- 42 months (range 1-264). Eighty-four leads were totally removed and two partially removed. For these two leads, the distal tip was not removed; in both cases the locking stylet was not secured at the distal electrode due to obstruction within the lead. Two patients developed arm edema following the procedure, which resolved with elevation. One patient developed a subclavian thrombosis, which resolved with warfarin anticoagulation. Four patients have expired due to unrelated causes. In conclusion, this intravascular approach for extraction of chronic leads is effective, and the procedure is safe when performed by experienced personnel.

Laser photoablation of ventricular tachycardia: correlation of diastolic activation times and photoablation effects on cycle length and termination--observations supporting a macroreentrant mechanism

Neodymium:yttrium-aluminum-garnet (YAG) photocoagulation during ventricular tachycardia allows the electrophysiologic effects of the temporal and spatial sequence of energy delivery to be correlated with local activation times. A retrospective analysis was performed of the termination of 19 episodes of ventricular tachycardia for which the local diastolic activation time was known for all successful ablation sites and for 95% of all ablation sites. The mode of termination was compared with that of 26 episodes of spontaneously terminating ventricular tachycardias. Spontaneous terminations occurred without a change in cycle length (54%) or with a 7 +/- 15% change in cycle length over one to three terminal beats (46%). In contrast, laser ablation-induced terminations resulted in a 39 +/- 55% increase in cycle length over nine or more cycles. The effect of attempted laser ablation was compared with the local presystolic activation time and the local activation time expressed as a percent of the diastolic interval (end of QRS complex = 0%, onset of next QRS complex = 100%). With one exception, no tachycardia terminated at ablation sites activating less than -50 ms before the QRS complex. All 8 successful first ablation attempts and 13 of all 19 successful ablations occurred in the 35% to 50% interval of diastolic activation. All successful ablations at sites activating at greater than 50% of the diastolic interval required multiple ablation attempts. Successful ablation was performed from the epicardium in 6 and from the endocardium in 13 episodes of ventricular tachycardia. These results are most consistent with a macroreentrant mechanism with a region of high vulnerability represented by the 35% to 50% interval of diastolic activation.(ABSTRACT TRUNCATED AT 250 WORDS)

Functional role of the epicardium in postinfarction ventricular tachycardia. Observations derived from computerized epicardial activation mapping, entrainment, and epicardial laser photoablation

BACKGROUND

Conventionally, monomorphic sustained ventricular tachycardia in patients with remote myocardial infarction is believed to originate from the subendocardium. In a previous study, we demonstrated that electrical activation patterns during ventricular tachycardia occasionally suggest a subepicardial rather than subendocardial reentry.

METHODS AND RESULTS

This study prospectively evaluated the functional role of the epicardium in postinfarction ventricular tachycardia with complex intraoperative techniques including computerized electrical activation mapping, entrainment, observation of changes in activation pattern during successful epicardial laser photoblation, and histological study. Five of 10 consecutive patients undergoing intraoperative computerized activation mapping had 10 ventricular tachycardia morphologies displaying epicardial diastolic activation These 10 "epicardial" ventricular tachycardias revealed the following global activation patterns: monoregional spread (two), figure-eight activation (five), and circular macroreentry (three). Entrainment of ventricular tachycardia using epicardial stimulation was successfully performed from an area of slow diastolic conduction in four tachycardia morphologies. During entrainment, global activation remained undisturbed with recordings showing a long stimulus to QRS interval, unchanged QRS morphology, and pacing capture of all components of the reentry circuit. Neodymium:yttrium aluminum garnet laser photocoagulation was delivered during ventricular tachycardia to epicardial sites of presumed reentry. Epicardial photoablation terminated five of five figure-eight tachycardias, two of three circular macroreentry tachycardias but not the monoregional tachycardias. Electrophysiological recordings during epicardial laser photocoagulation demonstrated progressive prolongation of ventricular tachycardia cycle length and apparent interruption of the presumed reentrant circuit. Histological evaluation of the reentrant region (three patients) showed a rim of surviving myocardium under the epicardial surface.

CONCLUSIONS

This study suggests that 1) chronic postinfarction ventricular tachycardia may result from subepicardial macroreentry, 2) slow conduction within the reentry circuit can be localized by computerized mapping and epicardial entrainment, and 3) ventricular tachycardia interruption by laser photocoagulation results from conduction delay and block within critical elements of the reentrant pathway. Viable subepicardial muscle fibers may constitute the underlying pathology.

Termination of ventricular tachycardia with epicardial laser photocoagulation: a clinical comparison with patients undergoing successful endocardial photocoagulation alone

Electrical activation-guided laser photocoagulation was used intraoperatively to terminate ventricular tachycardia in patients with ischemic heart disease. During ventricular tachycardia, laser irradiation was delivered to mapped sites with local diastolic activation. In 30 long-term survivors, 85 ventricular tachycardia configurations were terminated by ablation; 72 (84.7%) were terminated by endocardial photocoagulation. Thirteen (15.3%) required epicardial photocoagulation; however, these 13 ventricular tachycardias occurred in 10 (33%) of the 30 patients. An aneurysm was present in 70% of patients with successful endocardial photocoagulation, but in only 10% of patients requiring epicardial photocoagulation for at least one ventricular tachycardia configuration; 90% of all patients requiring epicardial laser photocoagulation had no aneurysm and had either a right or a left circumflex coronary artery-related infarction. In this group, epicardial activation data were similar to those described for ventricular tachycardia with an "endocardial" origin and included 1) delayed potentials during sinus rhythm, 2) presystolic or pandiastolic activation sequences during ventricular tachycardia, and 3) regions of block near the presumed region of reentry during ventricular tachycardia. This study suggests that the critical anatomic substrates supporting reentry in postinfarction ventricular tachycardia may occur at intramural or epicardial sites, particularly in patients with right or circumflex coronary artery-related infarction and no aneurysm.

The complex posterior septal space in the Wolff-Parkinson-White syndrome. Surgical experience with 47 patients

Forty-seven consecutive patients with the Wolff-Parkinson-White syndrome due to posterior septal accessory pathways were operated on from August 3, 1983 to March 23, 1989. Seven of these patients had Ebstein's anomaly, another three coronary sinus aneurysms, one a persistent left superior vena cava, and five others complex multiple pathway combinations. Two additional patients required surgery following unsuccessful catheter ablation and one after failed surgery at another institution. Thus nineteen of forty-seven patients (40%) had additional difficulty factors which tend to complicate the operative dissection in this already complex anatomical area. The surgical anatomy of the posterior septal space as well as the essential operative principles and techniques are reviewed. Each of the frequently encountered additional difficulty factors is described with emphasis on the coronary sinus aneurysm, a recently recognized entity.

Surgical treatment of arrhythmias

Surgical treatment of arrhythmias is often more expeditious and more cost-effective in the long run than pharmacologic therapy. In the past, surgical treatment of arrhythmias has been reserved for patients with disabling paroxysmal or incessant tachycardia refractory to medical management, severe life-threatening arrhythmia or aborted episodes of sudden death. However, tachyarrhythmias that are refractory to pharmacologic therapy because of drug inefficacy, noncompliance or limiting side effects are not uncommon. Although nonpharmacologic treatment of arrhythmias carries with it a one-time period of higher risk (i.e., when the patient undergoes surgery), it is curative and often preferable to the uncertainty and possibly higher cumulative risk associated with medical management.

Neodymium:YAG laser photocoagulation: a successful new map-guided technique for the intraoperative ablation of ventricular tachycardia

Neodymium:YAG laser photocoagulation was used in the intraoperative treatment of drug-resistant ventricular tachycardia (VT) in 17 consecutive patients. The cause of VT was previous myocardial infarction in 15, sarcoid in one, and idiopathic in one patient. Electrophysiologic studies were performed preoperatively, before hospital discharge, and 8 to 12 weeks and 1 year after surgery. At surgery, laser photocoagulation was performed on the normothermic heart during VT. Surgical mortality was 11.7%. There was one late nonarrhythmic death 35 days postoperatively. There were 55 VT morphologies. Laser successfully abated 52 of 55. Associated use of cryoablation was required in two of 55. One VT in the patient with sarcoidosis was not successfully ablated but was controlled by procainamide. In the long-term survivors with VT due to myocardial infarction the surgical cure rate was 100%, i.e., no spontaneous or inducible VT. Follow-up ranges from 6 to 18 months (mean 11.8 +/- 4.3). Nd:YAG laser photocoagulation is an effective addition to the operative treatment strategies for VT.

Technical considerations in the surgical approach to multiple accessory pathways in the Wolff-Parkinson-White syndrome

Surgical techniques for the approach to and division of atrioventricular accessory pathways have been designed and perfected during the past 18 years. The standard method of exposure of a single left free wall accessory pathway is by a left atriotomy. All other single accessory pathways are exposed through a right atriotomy. Up to twenty percent of patients with Wolff-Parkinson-White (WPW) syndrome harbor multiple atrioventricular accessory pathways. In this subgroup, classic operative techniques, especially the methods of approach, must be combined or modified depending on the specific locations of the accessory pathways encountered. Eighteen of 90 patients operated on for WPW syndrome at Charlotte Memorial Hospital from August, 1983, through September, 1986, had multiple accessory pathways. Thirty-eight of thirty-nine pathways were successfully divided. One posterior septal accessory pathway reappeared 2 months postoperatively and was catheter ablated. The most frequent combination of atrioventricular accessory pathways included a right free wall and a posterior septal accessory pathway (10 patients). This combination is approached by a right atriotomy. The posterior septal space dissection is extended onto the right free wall area. Technically the most difficult combination includes a left free wall and a posterior septal accessory pathway (3 patients in the present series). Our preferred approach is begun with a right atriotomy for the posterior septal space dissection, followed by an atrial septotomy to expose the left free wall area. There are other methods, however, that may be advantageous depending on the exact locations of the accessory pathways encountered.

Characteristics and clinical effects of myopotential signals in a unipolar DDD pacemaker population

Myopotential signals were recorded from atrial and ventricular leads during isometric exercise in 25 patients who had chronically implanted dual chamber pacemakers using the electrogram telemetry capability of the pacemakers. Average electrogram amplitude on the atrial channel was 0.92 mV (range 0.3 to 1.9) and on the ventricular channel was 0.98 mV (range 0.3 to 2.2); the difference was not significant. There was a strong correlation (R = 0.82) between the amplitude of myopotentials on the atrial and ventricular leads for individual patients. Myopotential sensing caused ventricular output inhibition in two patients (8%) and ventricular tracking in sixteen patients (64%). Pacemaker reprogramming abolished ventricular myopotential inhibition in all patients and stopped ventricular myopotential tracking in seven patients. We conclude that myopotentials can be analyzed and their effects ameliorated by a multiprogrammable pacemaker with electrogram telemetry capability.

Successful clinical laser ablation of ventricular tachycardia: a promising new therapeutic method

This preliminary report describes 5 consecutive patients operated on for drug-resistant ventricular tachycardia (VT). All were successfully treated with laser photocoagulation ablation alone. The continuous-wave neodymium:yttrium-aluminum garnet (Nd:YAG) laser (wavelength, 1.06 micron) was chosen because of its capability for controlled deep tissue penetration, which can be adjusted by manipulating the power and exposure time of the beam. All patients had severe coronary artery disease. Preoperative left ventricular ejection fractions were low (0.18 to 0.29). Risk factors associated with increased failure rates by conventional surgical approaches were frequent: absence of discrete left ventricular aneurysm (5 patients) and multiple VT morphologies with disparate sites of origin (4 patients). All patients recovered fully. VT was not inducible prior to discharge, and no patient was placed on a regimen of antiarrhythmic drugs. Current direct surgical approaches to drug-resistant VT have markedly improved operative results compared with indirect procedures. However, failures and mortality remain high. Laser photocoagulation obviates some of the problems associated with conventional methods. It is similar to cryotherapy in that the structural integrity of affected tissues is maintained. In contrast to cryosurgery, however, laser photocoagulation is achieved more rapidly and with more precise myocardial destruction. One of the most promising features of laser coagulation is that it is administered to the perfused normothermic heart. Consequently, each morphological form of induced VT is observed to disappear as its area of origin is systematically located by mapping and then ablated.

The effects of coronary revascularization on left ventricular function in ischemic heart disease

Although it is well established that coronary revascularization can reverse exercise-induced ischemic dysfunction, the effects on resting ventricular performance are controversial. From a group of 183 patients receiving surgical therapy for ischemic heart disease, 166 underwent bypass graft arteriography at an average of 7 to 14 days postoperatively. In 149 patients, satisfactory preoperative and postoperative biplane left ventriculograms were obtained. Regional wall motion was assessed by the 100 segment method of Sheehan and Dodge, and a perioperative change in shortening greater than 2 standard deviations of normal variability over 20 or more adjacent segments was considered significant. Ninety-five patients had stable or progressive angina, 88 had medically refractory unstable angina, 155 were in New York Heart Association Class IV, and 37 had a preoperative left ventricular ejection fraction of less than 0.4. Myocardial integrity was preserved with crystalloid cardioplegia and topical hypothermia. Seven hundred ninety-eight bypass grafts were performed (522 vein grafts and 276 mammary artery grafts), and 13 patients had concomitant left ventricular aneurysmectomy. Hospital mortality was 2.2%. The overall early graft patency rate was 95.9% (93.7% for vein grafts and 100% for mammary arteries). Only one patient had a decrement in regional wall motion, and 51 (37%) had significant postoperative improvement (27 in the unstable angina group and 24 in the stable angina group); in the patients with improved regional wall motion, ejection fraction increased by an average of 0.18 (p less than 0.01). Ejection fraction also improved after aneurysmectomy, and the increment seemed to result from both a reduction in end-diastolic volume and improved regional wall motion. Thus, reversible ischemic myocardial dysfunction appears to be common in the general population of patients undergoing coronary artery bypass grafting; 40% of patients with unstable angina and 34% of those with stable angina can be expected to have improved regional wall motion after successful revascularization. Finally, ventricular aneurysm resection significantly enhances left ventricular performance as assessed by ventriculographic ejection fraction.

Right ventricular isolation procedures for nonischemic ventricular tachycardia

Nonischemic ventricular tachycardia most commonly arises in the right ventricular free wall and is frequently refractory to medical therapy. Many different types of surgical procedures have been employed to treat medically refractory nonischemic ventricular tachycardia arising in the right ventricle, but the results of these procedures have been less than optimal. The majority of these surgical procedures have been directed toward ablation of the site (or sites) of origin of the tachyarrhythmia and have failed because of the frequent occurrence of multifocal or polymorphic ventricular tachycardia in these patients. We first employed localized surgical isolation procedures to control nonischemic ventricular tachycardia arising in the right ventricular free wall in 1979. These localized procedures evolved into the development of a technique for isolating the entire right ventricular free wall from the remainder of the heart to control ventricular tachyarrhythmias arising from multiple sites in the right ventricle. Case histories are reported of two patients who underwent localized isolation procedures in 1979 as well as two patients who underwent total disconnection of the right ventricle in 1982. The follow-up period in these four patients ranges from 2 to 5 years and the control of their tachyarrhythmias has been uniformly successful. However, surgical isolation of the entire right ventricular free wall has resulted in progressive dilatation of the right ventricle as documented by serial echocardiography. The pathophysiology of the progressive right ventricular dilatation postoperatively is discussed in terms of etiology and prevention, and the indications for application of localized and total isolation procedures for nonischemic right ventricular tachycardia are outlined.

Collateral conductance changes during a brief coronary occlusion in awake dogs

Function of the coronary collateral circulation during the course of a single abrupt coronary occlusion was evaluated in awake dogs instrumented over the long term. Studies were performed approximately 2 weeks after collateral development had been stimulated in the dogs by partial stenosis of the proximal left circumflex coronary artery. The pressure drop from the central aorta to the distal circumflex coronary artery was measured continuously. Under control conditions and at 30 sec and 4 min of a single abrupt complete circumflex occlusion, myocardial blood flow was determined by a radioactive microsphere technique. Coronary collateral conductance was calculated as mean collateral blood flow divided by the mean drop in pressure. The following was noted in dogs that developed collateral vessels: during the coronary occlusion, mean distal circumflex coronary pressure increased from 42 +/- 9 to 49 +/- 10 mm Hg (p less than or equal to .01); mean collateral flow increased from 0.78 +/- 0.30 to 0.84 +/- 0.33 ml/min/g (p less than or equal to .05); the endocardial/epicardial flow ratio increased from 0.77 +/- 0.36 to 1.04 +/- 0.25 (p less than or equal to .01); and the coronary collateral conductance increased significantly from 0.017 +/- 0.017 to 0.021 +/- 0.021 (ml/min/g)/mm Hg (p less than or equal to .005). These data suggest that during a brief occlusion of a major coronary artery, immature coronary collateral channels do not reach maximal function immediately after the occlusion. Rather, coronary collateral conductance increases with time and may be associated with improved transmural perfusion of the myocardium.

Increase in myocardial collateral blood flow during repeated brief episodes of ischemia in the awake dog

The purpose of this study was to determine whether coronary collateral blood flow changes in response to repeated brief periods of ischemia in dogs in which no attempt has been made to stimulate collateral vessel development. The dogs were instrumented with aortic and left atrial catheters and a balloon occluder on the left circumflex coronary artery and were studied in the awake state the following day. Blood flow to the collateral dependent myocardium was measured using 9 mu radioactive microspheres during four coronary occlusions of two minutes duration, each separated by one hour of reperfusion. A small but statistically significant increase in mean collateral blood flow was noted between the first and fourth occlusions; .03 to .05 ml/min/g. These data suggest that transient periods of brief ischemia may result in increases in collateral blood flow.

Surface electrocardiographic clues suggesting presence of a nodofascicular Mahaim fiber

Standard electrocardiograms from 87 consecutive patients with tachycardia of left bundle branch block configuration were analyzed retrospectively for features that might be characteristic of tachycardia utilizing a nodofascicular Mahaim fiber. The study group consisted of 13 patients with nodofascicular tachycardia, 34 with supraventricular tachycardia and aberrant conduction over the His-Purkinje system, 22 with ventricular tachycardia and 18 with antidromic tachycardia utilizing a right-sided accessory atrioventricular pathway. Six variables present during tachycardia of left bundle branch block configuration were predictive of a nodofascicular fiber: cycle length between 220 and 450 ms, QRS axis of 0 to -75 degrees, QRS duration 0.15 second or less, R wave in lead I, rS wave in precordial lead V1 and a precordial transition from a negative to a positive QRS complex after lead V4. All six criteria were present in 16 of the 87 patients. No patient with ventricular tachycardia satisfied these criteria, whereas 3 of 34 with supraventricular tachycardia, 1 of 18 with antidromic tachycardia and 12 of 13 with tachycardia using a nodofascicular fiber did. It is concluded that analysis of the surface electrocardiogram during tachycardia may suggest the presence of a nodofascicular fiber.

Adverse effects of nifedipine therapy on hypertrophic obstructive cardiomyopathy

A 62-year-old man with obstructive hypertrophic cardiomyopathy was given sublingual nifedipine, 10 mg, during invasive hemodynamic monitoring. After 15 minutes, his left ventricular outflow gradient increased from 22 to 80 mm Hg while arterial pressure fell from 152/70 to 122/64 mm Hg. Left ventricular end-diastolic pressure increased from 15 to 22 mm Hg. These adverse hemodynamic responses may have been a result of vasodilation of the peripheral circulation induced by nifedipine. Thus, some patients with hypertrophic obstructive cardiomyopathy may develop serious hemodynamic compromise when treated with nifedipine.

Myocardial blood flow distribution in concentric left ventricular hypertrophy

Regional myocardial blood flow during both control conditions and ischemia-induced vasodilatation was studied in eight chronically instrumented awake dogs. Seven of these animals had coarctation-banding of the ascending aorta performed at 6 wk of age, and the other dog had congenital subvalvular aortic stenosis. The mean left ventricular weight for the group was 157+/-7.6 g, and the left ventricular body weight ratio was 8.76+/-0.47 g/kg. None of the animals exhibited signs of congestive heart failure. During the control state, the mean left ventricular systolic pressure was 249+/-12 mm Hg and the left ventricular end-diastolic pressure was 11.5+/-0.5 mm Hg. The aortic diastolic pressure was 74+/-6 mm Hg. Mean left circumflex coronary artery blood flow was 71+/-6 cm(3)/min. In the animals with coarctation-banding, 52+/-6% of the flow occurred during systole. In the dog with congenital subvalvular aortic stenosis, 5% of the coronary flow was systolic. Mean transmural blood flow during resting conditions was 0.97+/-0.08 cm(3)/min per g, and the ratio of endocardial to epicardial flow (endo/epi) was 0.88+/-0.07. During reactive hyperemia, the mean transmural blood flow increased to 3.5+/-0.30 cm(3)/min per g; however, the endo/epi decreased to 0.52+/-0.06.THESE STUDIES DOCUMENT A DIFFERENCE IN TRANSMURAL BLOOD FLOW DISTRIBUTION BETWEEN THE NORMAL AND THE HYPERTROPHIED LEFT VENTRICLE: during resting conditions, in the normal ventricle, the highest flow occurs in the endocardial layer, whereas in the hypertrophied ventricle, the highest flow is in the middle layers with the endocardial flow less than the epicardial flow. During ischemia-induced vasodilatation, the abnormal endo/epi becomes accentuated markedly. These data demonstrate that, in situations requiring high flow, the endocardial layer of a heart with marked concentric left ventricular hypertrophy may not be perfused adequately.

A reproducible model of moderate to severe concentric left ventricular hypertrophy

A reproducible model for the production of moderate to severe concentric left ventricular hypertrophy has been developed in this laboratory. Coarctation-banding of the ascending aorta was performed successfully in 10 puppies. There were no late deaths related to aortic rupture, and in the dogs surviving for 1 yr no evidence of congestive heart failure was present. A second operative procedure was performed in seven dogs for chronic instrumentation, and all survived. Severe supravalvular aortic stenosis with a marked peak systolic pressure gradient was noted in each dog. Postmortem examination revealed a substantial increase in left ventricular mass and in the ratio of left ventricular to body weight.

Regional myocardial blood flow after sudden aortic constriction in awake dogs

Hemodynamic and regional myocardial blood flow responses were studied 5 seconds (early) and 30 seconds (late) after abrupt proximal aortic constriction in chronically instrumented awake dogs. During the early phase, left ventricular end-diastolic pressure (LVEDP) increased and stroke volume (SV) decreased significantly. During the late phase, there was a positive inotropic response manifested by a decrease in LVEDP and increase in SV (Anrep effect). The late inotropic response was closely associated with a recovery from subendocardial underperfusion. Hemodynamic and regional flow responses after beta-adrenergic blockade with propranolol (0.4 mg/kg) were similar to those observed during control. Studies during coronary vasodilation induced by adenosine (0.75--1.0 mg/kg per minute) showed that, if subendocardial flow was elevated during the early phase, the early increase of LVEDP and decrease of SV were less than control; however, if subendocardial flow did not change from control in the early phase and did not subsequently increase, there was no late inotropic response. These data suggest that the Anrep effect in the awake dog is closely related to a recovery from subendocardial ischemia.

The vectorcardiogram in right bundle branch block: correlation with cardiac failure and pulmonary disease

Frank vectorcardiograms (VCG) and clinical records of 243 patients with right bundle branch block (RBBB) were compared. The patients were classified into three categories on the basis of VCG criteria. The first category included 100 patients with a normal frontal axis, and the second category included 44 patients with concomitant left anterior hemiblock. The third category consisted of 99 patients with RBBB and myocardial infarction. The VCGs were classified into three types accoriding to the QRS configuration in the transverse plane. In type I the initial forces were anterior and counterclockwise and the afferent limb crossed the midline posterior to E point; in type II the initial forces were anterior and counterclockwise and the afferent limb crossed the midline posterior to E point; in type II the initial forces were anterior and counterclockwise and the afferent limb crossed the midline anterior to or through E point; and in type III the entire transverse loop was clockwise and anterior to E point. The patients were further classified according to the presence or absence of cardic failure or severe pulmonary disease. In patients with RBBB and a normal axis, cardiac failure or severe pulmonary disease was found in five of 49 patients wtih type I, 17 of 31 with type II, and 18 of 20 with type III pattern. In patients with RBBB and left anterior hemiblock, significant disease was found in one of 17 with type I, five of 16 with type II, and eight of 11 with type III pattern. These data show that, in patients with RBBB, the position of the afferent limb in the transverse plane can be used to predict cardiac failure or severe pulmonary disease.