Vincent A. Gaudiani

Routine enlargement of the small aortic root: a preventive strategy to minimize mismatch

BACKGROUND We routinely use aortic root enlargement (ARE) as part of one strategy to avoid prosthesis-patient mismatch in patients with relatively small aortic roots who are undergoing aortic valve replacement (AVR). METHODS We performed a retrospective review of 657 consecutive stented AVR patients at a single institution between 1995 to 2001. Of these, 114 (17%) patients underwent ARE. Root enlargement was selectively performed in patients at risk for prosthesis-patient mismatch, defined as calculated projected indexed effective orifice area (iEOA) less than 0.85 cm2/m2. This involved extension of the aortotomy between the left and noncoronary cusps, valve implantation, and Dacron patch closure of the aorta, thus permitting replacement with a valve size appropriate to body surface area. RESULTS The mean age of ARE patients was 72.5 +/- 11.0 years, with 32% aged 80 years or more. Of the patients, 61% were female and 27% had undergone previous cardiac operations. Combined procedures included coronary bypass in 57 patients and mitral repair or replacement in 24. The prevalence of mismatch was less than 3%. The ARE required an average of 19 minutes of additional aortic clamp time. The 30-day mortality was 0.9%. Logistic regression showed perfusion time to be the only independent predictor of mortality. CONCLUSIONS Our results show that ARE can be performed readily and with minimal added risk relative to standard AVR. We also present a preventive strategy to minimize mismatch predicted at time of operation from the reference value of effective orifice area for a given prosthesis and the patients size. This includes use of ARE to enhance the potential benefit of AVR.

Effect of duration of ventricular fibrillation on defibrillation efficacy in humans

The currently available automatic implantable cardioverter-defibrillator has proven highly successful for termination of ventricular tachycardia and fibrillation. Newer devices, however, permit lower energy shocks to be delivered initially and longer episodes of arrhythmia to occur before shocks are delivered. These changes may result in longer durations of arrhythmia before successful termination. Little is known about the effects of the duration of ventricular fibrillation on the efficacy of defibrillating shocks. In this study, we examined the efficacy of defibrillating shocks in 22 patients undergoing automatic implantable cardioverter-defibrillator implantation or generator change. Defibrillating shocks ranging from 300 to 600 V (5.9-24.2 J) were delivered in matched pairs after 5 and 15 seconds of ventricular fibrillation. For the 300-V shocks (5.9 J), defibrillation was accomplished in 82% of patients when the shocks were given after 5 seconds of ventricular fibrillation and in only 45% of patients when the shocks were delivered after 15 seconds (p less than 0.01). At higher energies, there was no difference in the efficacy of defibrillation shocks delivered after 5 compared with 15 seconds of ventricular fibrillation. The postshock aortic, systolic, and diastolic blood pressures were significantly lower when the shocks were given after 15 seconds of ventricular fibrillation than after only 5 seconds. We conclude that the duration of ventricular fibrillation affects defibrillation efficacy especially at energies that are relatively low compared with maximal device outputs and that longer episodes of ventricular fibrillation cause more postshock hemodynamic depression. These observations have implications for defibrillation threshold testing at the time of device implantation and for the design and programming of future automatic implantable antitachycardia devices.

PREOPERATIVE ERYTHROPOIETIN IN JEHOVAH'S WITNESSES WHO REQUIRE CARDIAC PROCEDURES

Abstract This report details the preoperative use of recombinant human erythropoietin in 2 Jehovahs Witnesses who required elective cardiac operations.

Comparison of defibriliation efficacy in humans using a new catheter and superior vena cava spring-left ventricular patch electrodes

The automatic implantable cardioverter-defibrillator currently utilizes an electrode system that requires a major operation for implantation. Effective defibrillation using an implantable cardioverter-defibrillator catheter positioned transvenously would eliminate the morbidity associated with such surgery. Fifteen patients undergoing defibrillator implantation were studied to compare the efficacy of the catheter with that of the superior vena cava spring (6.7 cm2, anode)-left ventricular patch (13.5 cm2, cathode) electrode system using truncated exponential waveforms with 60% tilt. The catheter is 11F in diameter and tripolar. A distal platinum-iridium tip used for pacing was separated by 4 mm from a middle 4.3 cm2 platinum electrode; these were positioned at the right ventricular apex. The proximal 8.5 cm2 platinum electrode was situated at the superior vena cava-right atrial junction. Defibrillation was performed using the middle (cathode) and proximal (anode) electrodes. Ventricular fibrillation was induced by alternating current six times, and defibrillation shocks of 1, 5, 10, 15, 20 or 25 J were given in random order, first using the catheter and then the spring-patch system. Rescue shocks of higher energy were given if there was failure. Although very low energy levels appeared to be slightly more efficacious when using the spring-patch system, there was no statistically significant difference between the electrode systems for any of the energies tested. Permanent implantation of the catheter would have been suitable in 45% of the patients, as compared with 54% of patients with the spring-patch system (p = NS).(ABSTRACT TRUNCATED AT 250 WORDS)

An Improved Technique for the Internal Mammary Artery Coronary Bypass Graft Procedure

Abstract An improved technique for internal mammary artery graft preparation is described. Following cautery dissection of the internal mammary artery (IMA) pedicle, the pedicle investing fascia is incised to the adventitial level along a single plane. This incision allows the tissue around the internal mammary artery to fall away and severs the muscular constrictions that often surround the internal mammary artery. Balloon calibration is performed to identify remaining constrictions and to relieve internal mammary artery spasm. A shear force limiting gauge insures that the exerted balloon force remains below the level demonstrated to cause intimal damage during electron microscopic studies. This technique allows full internal mammary artery distention without the devascularizing effects of full skeletonization. Distention of the distal internal mammary artery provides an enlarged hood to facilitate suture placement. Elongation of the internal mammary artery during balloon calibration aids in the performance of sequential grafts. This technique has been applied to 793 patients over the past five years. Postcalibration flow rates increased 3‐ to 18‐fold over precalibration flow rates. Two early occlusions occurred during this series, one due to endothelial strippage prior to the development and use of the shear force limiting gauge. Follow‐up showed 93.3% of patients to be asymptomatic. This combination of fascial incision and balloon calibration appears to offer safe technical and functional improvements to the performance of the internal mammary artery graft.

Transvenous catheter ablation of extranodal accessory pathways

Twelve patients with an accessory pathway and recurrent symptomatic reciprocating tachycardia or atrial fibrillation, or both, underwent attempted transvenous catheter ablation of the accessory pathway. In one patient with a small right coronary artery, the pathway was along the right free wall. In 11 patients, the pathway was located at or within 15 mm of the coronary sinus os. For these patients, a quadripolar electrode catheter was placed in the coronary sinus and positioned, if possible, so that the proximal pair of electrodes straddled the pathway. For those patients with a pathway greater than 5 mm within the coronary sinus, the most proximal electrode was placed at the os. This proximal pair of electrodes was connected to the cathodal output of a defibrillator with an anterior chest wall patch serving as the current sink. Two shocks were then delivered for a cumulative energy of 500 to 600 J (stored energy). Among the eight patients with a pathway at or within 5 mm of the coronary sinus os, conduction over the pathway was abolished in five and modified in one. Among the four patients with a pathway farther from the os (10 to 15 mm) and along the right free wall, pathway conduction was modified only in two. Rupture of the coronary sinus did not occur in any patient. There were no serious complications. Minor damage surrounding the area of ablation was seen at the time of surgical division of the accessory pathway in two of five patients with unsuccessful ablation who subsequently underwent surgery.(ABSTRACT TRUNCATED AT 250 WORDS)

Comparison of pre- and postoperative conduction patterns in patients surgically cured of atrioventricular node reentrant tachycardia

Patients with atrioventricular (AV) node reentrant tachycardia characteristically have short and constant retrograde His-atrium conduction times (H2A2 intervals) during the introduction of ventricular extrastimuli. It has therefore been suggested that the tachycardia circuit involves retrograde conduction up an accessory pathway located in perinodal tissue. If the mechanism of surgical cure of AV node reentrant tachycardia is interruption of this accessory pathway, postoperative changes in retrograde conduction would be expected. Thirteen patients with drug-refractory AV node reentrant tachycardia underwent surgery. Preoperatively, H2A2 intervals were short and constant. During AV node reentrant tachycardia, earliest atrial activation was seen near the His bundle and was 0 to 25 ms before ventricular activation in all patients except one. Surgery consisted of dissection of right atrial septal and anterior inputs to the AV node and central fibrous body. Postoperatively, the H2A2 interval remained short and constant compared with preoperative values although it was slightly prolonged (74 +/- 18 versus 61 +/- 21 ms, p less than 0.005). Twelve of the 13 patients are free of tachycardia after 28 +/- 13 months and no patient has had evidence of AV node block. Thus, surgical cure of AV node reentrant tachycardia is highly successful; however, there is no reason to postulate an accessory pathway or use of perinodal tissue as part of the tachycardia circuit and the mechanism of surgical success remains obscure.

Mitral valve operations through standard and smaller incisions.

OBJECTIVE Evaluate the operative results of mitral valve repair (MVV) and mitral valve replacement (MVR) performed through standard and smaller incisions. METHODS From January 1997 through December 2002, 821 consecutive patients underwent mitral valve operation. Of these procedures, 475 were MVV and 346 were MVR. A logistic regression model was developed to identify the risk factors for early mortality and to evaluate the effect of replacement versus repair and standard versus small incision. RESULTS Replacement patients were older, more likely New York Heart Association (NYHA) class III or IV, more likely female, and had more frequent previous median sternotomy and stroke (all P <.05). The mitral diagnoses in the 2 groups were markedly different. Prolapse and ischemia dominated the repairs, whereas calcific and rheumatic diagnoses required replacement. There were 667 concomitant procedures performed on these patients, most commonly coronary artery bypass graft (229), aortic valve replacement (170), maze (79), and tricuspid valve (TV) repair/replacement (73). Thirty-three patients (4.0%) died in the postoperative period, 2.3% after repair and 6.4% after replacement ( P <.01). Endocarditis (4/17), calcific disease (7/73), and ischemic disease (9/121) accounted for 26% of patients and 60% of deaths. Multivariate regression analysis identified NYHA class, emergent status, concomitant TV operation, and history of renal failure, but not repair versus replacement, as independent risk factors predicting mortality. We estimated that 356 of the 821 patients (43%) were candidates for small-incision operations, the others were excluded by the need for concomitant procedure or other cause. A total of 205/356 (57%) actually underwent small-incision operations, all with central cannulation and standard techniques. From 1997-1999, 32% of eligible patients were so treated, but from 2000-2002, with increasing surgeon experience, this percentage rose significantly to 71% ( P <.01). Eligible patients who underwent small-incision operation were younger and had lower NYHA classifications, lower preoperative creatinine, and shorter length of stay (all P <.01) than those who had standard incisions. Cross-clamp time, perfusion time, and mortality rate were not significantly different. CONCLUSIONS The mortality rate for MV operations is concentrated among a few diagnoses. In some patients surgery may be approached safely through smaller incisions without introducing new elements of operative risk.

Left main coronary artery reconstruction after radiation therapy

We report the case of a patient with radiation-induced left main coronary stenosis in whom an internal mammary artery bypass graft failed a 5 years and necessitated direct left main reconstruction.

The Risks and Benefits of Reoperative Aortic Valve Replacement

BACKGROUND Many patients are advised to have mechanical aortic valve replacement (AVR) because their expected longevity exceeds that of tissue prostheses. This strategy may avoid the risks of reoperation but exposes patients to the risks of long-term anticoagulation therapy. Which risk is greater? METHODS We reviewed the records of 1213 consecutive, unselected AVR patients, 60% of whom had concomitant procedures, who were treated from 1994 through 2002. Of these patients, 887 were first-time AVR patients, and 326 underwent reoperation. Of the reoperation patients, 134 had previously undergone AVR (redo). We constructed a risk model from these 1213 cases to assess the factors that predicted mortality and to examine the extent to which reoperation affected outcome. RESULTS Multiple logistic regression analysis indicated that factors of reoperation and redo operation did not predict mortality. In fact, the mortality rate was 4.1% for all first AVR operations and 3.1% for all reoperation AVR ( P =.891). Significant predicting factors (with odds ratios) were reoperative dialysis (6.03), preoperative shock (3.68), New York Heart Association class IV (2.20), female sex (1.76), age (1.61), and cardiopulmonary bypass time (1.26). CONCLUSIONS In this series, the risk of reoperation AVR is comparable with the published risks of long-term warfarin sodium (Coumadin) administration after mechanical AVR. Any adult who requires AVR may be well advised to consider tissue prostheses.