Clinical benefits of endoscopic vein harvesting in patients with risk factors for saphenectomy wound infections undergoing coronary artery bypass grafting.

OBJECTIVE: The influence of endoscopic harvesting techniques on the prevalence of leg-wound complications after coronary artery bypass grafting remains to be defined for patients at high risk for the development of wound infections. METHODS: Among 1473 patients undergoing coronary artery bypass grafting who had the saphenous vein harvested by either a continuous incision or skip incisions leaving intact skin bridges, we determined the prevalence of wound infections to be 9.6%. The following variables were entered into logistic regression analysis to identify significant risk factors that might be predictive of wound infection: diabetes, peripheral vascular disease, obesity, renal failure, steroid use, age, sex, and type of closure. We then prospectively randomized 132 patients found to be at high risk of wound infection to either endoscopic vein harvesting or a continuous open incision. RESULTS: Univariate analysis showed female sex (P =.04), diabetes (P <.001), and obesity (P <.001) to be predictors of wound infection. In a multivariate model diabetes (P =.02) and obesity (P =.001) were independent predictors. In patients at high risk, the prevalence of wound infection was 4.5% for the endoscopic group versus 20% for the open group (P =.01). Vein procurement time was greater in the endoscopic group (65 minutes vs 32 minutes, P <.001), as was the number of vein repairs required (2.5 vs 0.6, P <.001). CONCLUSION: The use of endoscopic vein harvesting decreases the prevalence of postoperative leg-wound infections in high-risk patients with diabetes and obesity. Whether this translates into an economic benefit that justifies the additional cost of that technology requires further analysis.

Placement of a permanent epicardial pacemaker in children using a subcostal approach.

BACKGROUND: Previously described techniques for epicardial pacemakers in children have generally included either a left thoracotomy approach or a subxiphoid incision. METHODS: We have recently used a single left subcostal incision for placement of both the epicardial electrodes and the pacemaker generator. We report our initial experience with this technique in 8 patients. The mean age was 4 years (range, 4 months to 12 years). The smallest patient weighed 4,100 g. RESULTS: The subcostal approach was successful in 7 patients. One patient with a narrow costal margin operated on early in our experience required conversion to a thoracotomy. The pacing thresholds were uniformly excellent in all patients. There have been no associated complications. CONCLUSIONS: Placement of epicardial leads using a left subcostal incision avoids a thoracotomy, is simpler than a subxiphoid approach, and results in acceptable thresholds with minimal morbidity.

Repair of coarctation of the aorta during infancy minimizes the risk of late hypertension.

BACKGROUND: Recent surgical reports on coarctation of the aorta have primarily focused on the relative merits of various operative techniques. However, appropriate timing for elective repair remains unclear. METHODS: In a retrospective analysis we examined the surgical outcomes in 176 consecutive patients undergoing repair of coarctation of the aorta in our institution over a 25-year period. Ninety-nine percent of the patients had follow-up for a median of 7.5 years. RESULTS: A total of 13 patients have died (7.4% overall mortality). Nine of these patients had associated complex intracardiac anomalies. There was no mortality in the 113 patients with isolated coarctation. Residual or recurrent coarctation occurred in 27 patients (15.3%). The age at operation and the type of surgical repair did not have an effect on the incidence of recurrence. Persistent or late hypertension was identified in 18 of the 107 patients who have been followed up for more than 5 years (16.8%). A total of 48 patients operated on during infancy have been followed up for more than 5 years. Only 2 have developed late hypertension (4.2%). Both of these patients had recurrence. In contrast, 16 of the 59 patients operated on after a year of age had late hypertension (27.1%). CONCLUSIONS: To minimize the risk of persistent hypertension, elective repair of coarctation should be performed within the first year of life.

Carotid occlusive disease and stroke risk in coronary artery bypass graft surgery.

To clarify the perioperative stroke risk in patients with carotid stenosis or occlusion having coronary artery bypass graft (CABG) surgery, we retrospectively reviewed the records of 1,022 patients who had CABG during a 2-year period (1992, 1993). Of these, 224 had preoperative carotid duplex studies, usually for bruit or remote symptoms. We analyzed clinical and neuroimaging findings for all patients who had strokes to determine infarct topography and presumed mechanism, either low perfusion or embolism. Perioperative stroke was always ipsilateral to severe (> or = 70%) carotid disease, and occurred in 2 (8.0%) of 25 patients with carotid occlusion, 3 (50.0%) of 6 patients with 70 to 99% stenosis, and 9 (4.7%) of 193 patients with less than 70% stenosis. Borderzone infarcts occurred with all degrees of carotid stenosis. Stroke frequency had a positive correlation with the degree of carotid stenosis. Eight (1.0%) of the 798 patients not studied by carotid duplex had stroke in various vascular distributions. Overall, stroke occurred in 22 (2.2%) of the 1,022 patients having CABG surgery. Our results suggest that while the overall risk of perioperative stroke in CABG surgery is low, the risk is increased in patients with severe extracranial carotid stenosis or occlusion. The role of carotid disease and the mechanism of borderzone infarction in CABG surgery remain unsettled.

Treatment of multiple cerebral emboli from an ulcerated, thrombogenic ascending aorta with aortectomy and graft replacement.

Multiple studies link aortic arch atheroma as a donor site for cerebral emboli. However, treatment of this condition remains controversial. We report a patient with recurrent brain emboli from an ulcerated, thrombogenic aorta treated with aortectomy and graft replacement.

Surgical treatment of systemic atheroembolism from the thoracic aorta.

BACKGROUND: Surgical procedures performed exclusively for atheroembolic events arising from the thoracic aorta rarely have been reported. Presented here are 2 patients who underwent successful operation for these problems. METHODS: The clinical presentation, diagnostic evaluation and surgical approach to 2 patients with different embolic sources in the thoracic aorta are presented. One patient had experienced three strokes and was noted by multiplane transesophageal echocardiography to have protruding atheromas with ulcerations in the transverse arch and origin of the brachiocephalic vessels. The transverse arch was replaced using hypothermic circulatory arrest with individual reimplantation of the brachiocephalic vessels. The second patient presented with "blue toe" syndrome from mobile atheromas in the mid-descending thoracic aorta defined by transesophageal echocardiography. A localized debridement was performed using simple aortic cross-clamping. RESULTS: Both patients had uneventful postoperative courses and had no further atheroembolic events. CONCLUSIONS: When standard diagnostic modalities do not delineate an embolic source for either stroke or peripheral embolization, transesophageal echocardiography is recommended as an excellent means of identifying atheromas in the thoracic aorta that could be the source for emboli. Once these lesions are identified, a surgical procedure should be performed to prevent further embolization.

Excision of a pulmonary valve abscess in a 61-year-old woman with single ventricle.

A 61-year-old woman with levo-transposition of the great arteries, double-inlet single left ventricle, and valvar and subvalvar pulmonary stenosis presented with a large pulmonary valve vegetation unresponsive to antibiotic therapy. The diagnostic evaluation and the surgical management are discussed. At operation the pulmonary valve was excised and an abscess cavity was obliterated with a pericardial patch. She is currently doing well 3 years after the operation.

Lung dose estimates from air sampling and bioassay data--a comparison.

Occupational monitoring data are typically in the form of air samples or biological samples. Air samples are more frequently available and often have been used to characterize personnel exposure in epidemiological studies. Air samples that are not specific to individual employees are easier and cheaper to procure than biological samples such as urinalyses. However, the correlation between concurrent air samples and urinalyses has not always been found to be strong. The purpose of this paper is to compare internal radiation doses for uranium workers estimated from air sample results with those estimated from urine sample results. The comparison was made on results associated with individuals who worked in a uranium processing and fabrication facility between 1950 and 1956. Independent lung dose estimates were made for individuals for whom both types of data were available for periods of 300-365 d. Plots of the data and statistical analyses failed to show evidence of correlation of any practical significance between the data generated by the two methods. A number of unquantifiable variables were enumerated for both types of estimates. It is concluded that within this study (1) only minimal correlation was demonstrable between lung doses based on air monitoring and doses based on urinalysis data because of the number of such variables affecting the measurements; and (2) general air data would not be the most useful measure of exposure upon which to base lung dose estimates.

Postoperative cardiothoracic infection: diagnostic value of indium-111 white blood cell imaging.

During a 6.5-year period, 50 indium 111-labeled white blood cell scans were obtained in 49 selected patients who had undergone sternotomy. Retrospectively, six sternal wounds and eight cardiovascular prostheses were found to be infected in 13 patients. For cardiothoracic surgical sites, the sensitivity, specificity, and accuracy of indium-111-labeled white blood cell scintigraphy were 86%, 97%, and 95%, respectively. Whole-body imaging identified the presence of major extramediastinal sites of infection in 10 patients. In patients with complicated cardiothoracic conditions, indium-111-labeled white blood cell imaging provides valuable diagnostic information regarding a variety of postoperative infections.

Cryopreserved aortic homografts contain viable smooth muscle cells capable of expressing transplantation antigens.

Frozen aortic tissue is increasingly used as homografts in reconstructive cardiovascular surgical procedures. The viability of cells within these cryopreserved tissues, their identity, and their potential immunogenicity have been the subject of controversy. We cultured cells from cryopreserved human aortic homografts that reacted with a monoclonal antibody that recognizes muscle actin isoforms, identifying them as smooth muscle cells. Under basal conditions, these smooth muscle cells contained messenger ribonucleic acid for class I human leukocyte antigens detected by northern blotting and expressed class I human leukocyte antigen on their surfaces as measured by enzyme-linked immunoassay and immunohistochemistry. Unstimulated smooth muscle cells contained no class II human leukocyte antigen messenger ribonucleic acid as determined by northern blotting and displayed almost no class II surface antigen as determined by enzyme-linked immunoassay. Interferon gamma (1000 U/ml, 72 hours), a product of activated T lymphocytes, not only increased the expression of class I human leukocyte antigens by smooth muscle cells, but induced class II human leukocyte antigen messenger ribonucleic acid and elevated surface expression from 22 +/- 7 to 819 +/- 35 enzyme-linked immunoassay units (n = 4). Immunohistochemistry revealed few class II-positive smooth muscle cells under basal culture conditions, but all cells showed high levels of DR antigen after exposure to interferon gamma for 3 days. Similar results were obtained in two independent isolates. We conclude that cryopreserved aortic homografts can contain viable smooth muscle cells capable of expressing major histocompatibility antigens that might render them immunogenic and susceptible to rejection by the recipient's immune system.

Clinical and hemodynamic performance of the 19-mm Carpentier-Edwards porcine bioprosthesis.

Because of concerns about the hemodynamic performance of 19-mm porcine valves, we retrospectively reviewed the clinical results and echocardiographic studies of 52 consecutive patients who received a 19-mm Carpentier-Edwards porcine bioprosthesis (model 2625) for aortic valve replacement from 1986 through 1991. Nearly 87% of the patients were women, the mean age was 69 years, and the mean body surface area was 1.63 +/- 0.27 m2. Seventy-three percent of the patients had pure aortic stenosis, 96% were in New York Heart Association classes III and IV, and 56% underwent urgent or emergent operation. Overall hospital mortality was 7.7% with a late mortality of 8.3% at a mean follow-up of 25 +/- 18 months. No patient experienced a valve-related complication, and 95% of surviving patients were in New York Heart Association classes I and II. Two-dimensional and Doppler echocardiography performed during the first postoperative week revealed a maximal instantaneous gradient of 44.7 +/- 13.0 mm Hg. In 43 patients for whom additional data were available, the mean gradient was 26.4 +/- 8.2 mm Hg with an effective orifice area of 0.85 +/- 0.18 cm2. This study defines the normal range of postoperative gradients across the 19-mm Carpentier-Edwards porcine valve and demonstrates that patients receiving this valve can achieve significant clinical improvement despite the presence of high transvalvular gradients measured by echocardiography.

Restoration of the pulmonary valve reduces right ventricular volume overload after previous repair of tetralogy of Fallot.

BACKGROUND: Severe pulmonary regurgitation (PR) and associated right ventricular (RV) dilatation are late complications of surgical repair of tetralogy of Fallot (TOF). For the past several years, we have restored pulmonary valve competence with the exclusive use of cryopreserved allografts. METHODS AND RESULTS: Sixteen patients with symptoms of diminished exercise tolerance and echocardiographic evidence of progressive PR with severe RV dilatation underwent placement of allografts in the RV outflow tract at a median age of 12 years (10 years after TOF repair). Abnormal exercise tolerance tests were documented in 10 patients. Additional surgical procedures included pulmonary artery augmentation (n = 6), closure of residual left to right shunts (n = 3), and subendocardial resection for monomorphic ventricular tachycardia (n = 1). Six patients had either preoperative or postoperative balloon dilations of pulmonary artery stenoses. All patients had symptomatic improvement after allograft insertion. At a mean follow-up of 26.4 +/- 3.4 months, the severity of PR improved in all but one patient. In 12 patients (group 1), conduit regurgitation was either trace (n = 11) or mild (n = 1). Four patients (group 2) had moderate conduit regurgitation. In a retrospective analysis, pulmonary artery diameters and cross-sectional areas were significantly smaller in the group 2 patients compared with the group 1 patients. With the exception of one patient, RV end-diastolic diameter (RVEDD/BSA) fell after allograft insertion in each patient (P < .01). The reduction in RVEDD/BSA was significantly greater in group 1 than in group 2 (31.8 +/- 3.4% versus 21.4 +/- 11.0%, P < .05). CONCLUSIONS: Thus, restoration of the pulmonary valve with cryopreserved allografts improved exercise tolerance and diminished RV volume overload in patients with severe PR after previous repair of TOF. Optimal results were achieved in patients who did not have significant residual pulmonary artery distortion.

Human coronary transplantation-associated arteriosclerosis. Evidence for a chronic immune reaction to activated graft endothelial cells.

Occlusive disease of coronary arteries of engrafted hearts is the major obstacle to long-term survival of human cardiac allografts. The pathogenesis of this process remains uncertain. The identity and localization of cells found in transplantation-associated arteriosclerosis lesions from human cardiac allografts were evaluated, and their expression of class II major histocompatibility complex (human leukocyte antigen-DR [HLA-DR]), surface molecules required for recognition of foreign cells by CD4+ T lymphocytes, was noted. Expanded intimas of transplanted coronary arteries contain T lymphocytes (both CD4+ and CD8+ in approximately equal number) and HLA-DR+ macrophages, both localized primarily in a ring immediately below the luminal endothelium, a distribution strikingly different from that in typical atherosclerosis. Coronary arterial endothelium from six of six transplanted hearts studied bore high levels of HLA-DR. Normal human arteries or usual atherosclerotic lesions have few if any HLA-DR+ endothelial cells. The significance of these findings was tested by evaluating the ability of HLA-DR+ arterial cells to interact with allogeneic T cells in vitro. Endothelial cells (but not smooth muscle cells) cultured from human arteries stimulated foreign CD4+ T cells to proliferate and augmented their secretion of interleukin-2. These findings suggest that ongoing stimulation of recipient T lymphocytes by HLA-DR+ endothelium of donor coronary arteries contributes to a sustained regional immune response. Consequent local release of cytokines may regulate smooth muscle cell proliferation and matrix accumulation within the coronary arteries of allografted hearts.

Total lymphoid irradiation and discordant cardiac xenografts.

Total lymphoid irradiation can prolong concordant cardiac xenografts. The effects of total lymphoid irradiation in a discordant xenograft model (guinea pig to rat) were studied with and without adjuvant pharmacologic immunosuppression. Inbred Lewis rats were randomly allocated to one of four groups. Group 1 (n = 6) served as a control group and rats received no immunosuppression. Group 2 (n = 5) received triple-drug therapy that consisted of intraperitoneal azathioprine (2 mg/kg), cyclosporine (20 mg/kg), and methylprednisolone (1 mg/kg) for 1 week before transplantation. Group 3 animals (n = 5) received 15 Gy of total lymphoid irradiation in 12 divided doses over a 3-week period. Group 4 (n = 6) received both triple-drug therapy and total lymphoid irradiation as described for groups 2 and 3. Complement-dependent cytotoxicity assay was performed to determine if a correlation between complement-dependent cytotoxicity and rejection-free interval existed. Rejection was defined as cessation of graft pulsation and was confirmed by histologic test results. Only groups 1 and 2 showed a difference in survival (group 1, 6.9 +/- 1.0 minutes; group 2, 14.2 +/- 2.7 minutes, p = 0.02). Although total lymphoid irradiation did decrease complement-dependent cytotoxicity, linear regression revealed no correlation between complement-dependent cytotoxicity and graft survival (coefficient of correlation, 0.30). Unlike concordant cardiac xenografts, total lymphoid irradiation with or without triple-drug therapy does not prolong graft survival.

Effects of atrial cardioplegia on the ischemic right ventricle after acute coronary artery occlusion and reperfusion.

Right atrial cardioplegia has been advocated as a simple method of delivering retrograde cardioplegia. Passive distention of the right heart inherent with right atrial cardioplegia has been shown to impair right ventricular function in a canine model of global ischemia. This study was designed to compare right ventricular performance after right atrial cardioplegia administered intermittently (n = 5) and continuously (n = 5) with coronary sinus retrograde cardioplegia (n = 5) and aortic root cardioplegia (n = 8) in a canine model of acute right ventricular ischemia and reperfusion. Right ventricular performance was assessed using the load-independent relationship of end-systolic pressure versus dimension (myocardial fiber length). Right ventricular performance was well preserved after reperfusion in those dogs protected with intermittent right atrial cardioplegia (95% of control). Results with continuous right atrial cardioplegia (66% of control) and coronary sinus retrograde cardioplegia (40% of control) demonstrated diminished postreperfusion right ventricular performance. Right ventricular performance in the group protected with aortic root cardioplegia was significantly impaired after reperfusion when compared with all retrograde groups (34% of control, p less than 0.05). In this model, postreperfusion right ventricular performance was preserved in the right atrial cardioplegia groups despite passive ventricular distention. All methods of retrograde cardioplegia resulted in superior preservation of right ventricular performance when compared with standard aortic root cardioplegia.

Clinical and hemodynamic performance of the Ionescu-Shiley valve in the small aortic root. Results in 117 patients with 17 and 19 mm valves.

The Ionescu-Shiley pericardial valve was our bioprosthetic valve of choice between 1981 and 1985 for patients in whom the aortic anulus could not accept a valve larger than 19 mm in outer diameter or in whom the avoidance of warfarin sodium (Coumadin) was important. A series of 117 consecutive patients who received 17 or 19 mm valves for isolated aortic valve replacement or aortic valve replacement combined with coronary artery bypass grafting or other valvular procedures was analyzed. Overall, 74% of the patients were female, with a mean age of 70.9 years and a body surface area of 1.67 +/- 0.19 m2; 92.3% were in New York Heart Association class III-IV, and the operation was urgent or emergent in 46%. The operative mortality rate was 7.7%, with no deaths in patients undergoing isolated elective first-time aortic valve replacement. Mean follow-up for survivors was 2.5 years (10 to 62 months). There were 20 late deaths, of which three were valve related, three were due to sudden death or arrhythmias, and two were due to persistent heart failure. The actuarial survival rate at 5 years was 68%. Clinical follow-up revealed a low incidence of valve-related complications, and 96.4% of survivors were in class I-II. Postoperative echocardiography before hospital discharge revealed a maximum instantaneous gradient of 18.4 +/- 3.0 mm Hg in five patients having a 17 mm valve and 31.3 +/- 12.7 mm Hg in 20 patients having a 19 mm valve. Doppler echocardiography was performed in 22 patients at a mean follow-up of 39.3 +/- 11.7 months. The maximum instantaneous gradient was 25 +/- 17.2 mm Hg for 17 mm and 17.41 +/- 5.4 mm Hg for 19 mm valves at late follow-up. The effective orifice area was 0.85 +/- 0.1 cm2 for 17 mm and 1.21 +/- 0.21 cm2 for 19 mm valves. This study defines the normal range of Doppler echocardiographic transprosthetic gradients for the Ionescu-Shiley valve and confirms that low operative mortality and excellent clinical improvement can result from the use of small Ionescu-Shiley valves in elderly patients despite moderate postoperative transvalvular gradients.

Functions of vascular wall cells related to development of transplantation-associated coronary arteriosclerosis.

The accelerated form of arteriosclerosis that occurs in the coronary circulation of transplanted hearts currently presents a major limitation to the long-term success of this therapy. The pathogenesis of this lesion is unclear. Recent advances in vessel wall biology have disclosed interplay between mediators of the immune response and functions of vascular cells of potential significance in the formation of this accelerated form of arterial disease. We hypothesize that the development of accelerated arteriosclerosis in the arteries of transplanted hearts represents a form of chronic immunologic reaction resembling delayed-type hypersensitivity localized in the graft's arteries, a manifestation of cellular immunity mediated in large part by a regionally acting cytokine network. We emphasize the active responses of intrinsic vessel wall cells, including inappropriate expression of HLA and the likely participation of cytokines derived from vascular cells as well as from infiltrating leukocytes in amplification and propagation of this localized chronic immune reaction. This mechanism, which involves helper T cells interacting with class II HLA, may distinguish transplantation-associated arteriosclerosis from typical acute rejection, which may involve primarily cytolytic T cells interacting with class I HLA. Lesions of the common variety of atherosclerosis manifest certain features of immune activation. Therefore, we further hypothesize that the transplantation-associated form represents an extreme case of processes that also contribute to usual coronary atherosclerosis. For this reason, study of the accelerated disease may aid understanding of atherogenesis in general. Unraveling the basic pathobiology of these clinically important arterial diseases should lay the groundwork for rational design of selective therapeutic strategies to prevent or retard their development.

Protective effects of retrograde compared with antegrade cardioplegia on right ventricular systolic and diastolic function during coronary bypass surgery.

The effect of retrograde cardioplegia delivered through the right atrium on right ventricular performance has not been critically examined in humans. We randomized 20 patients with right coronary artery lesions to receive cold blood cardioplegia solution either retrograde through the right atrium (group 1, n = 10) or antegradely (group 2, n = 10). The patients were similar in age, sex, severity of coronary artery disease, cross-clamp time, and completeness of revascularization. Before operation, right ventricular function was assessed by radionuclide ventriculography, and 18-24 hours after operation, right ventricular volumes and performance were assessed at a constant-paced heart rate by simultaneous hemodynamic-radionuclide measurements, before and after a fluid challenge. Intraoperative right ventricular temperatures were not different between the groups. Right ventricular volumes and ejection fractions were not different at baseline. After operation, at similar heart rates and loading conditions, there was a trend for the antegrade group to increase right ventricular end-systolic volume (p less than 0.1) whereas the retrograde group had no change in this parameter from the preoperative state. Postoperative ventricular function curves (p = NS, retrograde versus antegrade) suggest equivalent systolic performance in both groups. Right ventricular diastolic performance showed no significant differences between the two groups, suggesting no detriment to compliance due to right ventricular distension during operation. This suggests that retrograde cardioplegia adequately protects the right ventricular myocardium during bypass surgery and may be used as an alternative procedure in situations where ventricular cooling is inadequate with antegrade delivery due to severe coronary artery disease or aortic valvular disease.

Left ventricular inotropic effect of atrial pacing after coronary artery bypass grafting.

The effect of atrial pacing on left ventricular (LV) performance was studied in 19 patients, 24 hours after coronary artery bypass grafting (CABG). LV volumes were calculated from simultaneous radionuclide-thermodilution measurements at rest (heart rate 82 +/- 12 beats/min), 10 minutes after the start of atrial pacing (100 beats/min), and with atrial pacing plus volume loading to return preload toward baseline. Atrial pacing reduced preload as reflected by LV end-diastolic volume index (69 +/- 14 vs 60 +/- 14 ml/m2, mean +/- standard deviation) (p less than 0.0001), but returned to baseline with volume loading. Afterload, as reflected by arterial end-systolic pressure, did not change with atrial pacing (63 +/- 9 at baseline vs 64 +/- 8 mm Hg with pacing, difference not significant). Afterload increased with volume loading (68 +/- 10 mm Hg, p less than 0.025 vs baseline and pacing). LV stroke volume decreased with atrial pacing due to reduced preload, but returned to baseline with volume loading. Cardiac index increased with atrial pacing and increased further with volume loading. Compared with baseline, LV end-systolic volume index was reduced during atrial pacing both before and after volume loading, despite unchanged or augmented afterload. The combination of atrial pacing and volume loading resulted in augmentation of LV stroke work, despite no increase in preload compared with baseline. Thus, after CABG, increased (paced) heart rate augments inotropic state, as indicated by reduced LV end-systolic volume under conditions of unchanged or increased afterload, and elevated LV stroke work without an increase in preload or a decrease in afterload.

Use of self-adhesive external defibrillator pads for complex cardiac surgical procedures.

We describe a useful technique for the management of life-threatening arrhythmias that occur during complex or reoperative cardiac surgical procedures when internal defibrillation cannot be achieved. Two self-adhesive external pads are attached to the patient before draping to enable the delivery of current for defibrillation or cardioversion without the need for removal of adhesive surgical drapes and the cumbersome use of external defibrillator paddles.