Ventricular Pacing Wires Research Articles

Abstract 273: Noninvasive Mitochondrial Modulation: Neuroprotection in a Translational Model of Cardiac Arrest and Resuscitation

Background: Mitochondrial dysfunction contributes to cardiac arrest induced brain injury and has been a target for neuroprotective therapies. An emerging concept suggests that hyperactivation of neuronal mitochondria following resuscitation results in hyperpolarization of the mitochondrial membrane during reperfusion, which drives generation of excess reactive oxygen species. Previous studies from our group demonstrated that limiting mitochondrial hyperactivity by non-invasively modulating mitochondrial function with specific near infrared light (NIR) wavelengths can reduce brain injury in small animal models of global and focal ischemia. Hypothesis: Inhibitory wavelengths of NIR will reduce neuronal injury and improve neurocognitive outcome in a clinically relevant swine model of cardiac arrest. Methods: Twenty-eight male and female adult swine were enrolled (3 groups: Sham, CA/CPR, and CA/CPR + NIR). Cardiac arrest (8 minutes) was induced with a ventricular pacing wire and followed by manual CPR with defibrillation and epinephrine every 30 seconds until return of spontaneous circulation (ROSC), 2 of the 20 swine that underwent CA did not achieve ROSC and were not enrolled. Treatment groups were randomized prior to arrest and blinded to the CPR team. Treatment was applied at onset of ROSC by irradiating the scalp with 750 nm and 950 nm LEDs (5W) for 2 hours. Results: Sham-operated animals all survived (8/8), whereas 22% of untreated animals subjected to cardiac arrest died within 45 min of ROSC (CA/CPR, n= 7/9). All swine treated with NIR survived the duration of the study (CA/CPR + NIR, n=9/9). Four days following cardiac arrest, neurological deficit score was improved in the NIR treatment group (50 ± 21 CA/CPR vs. 0.8 ± 0.8 CA/CPR + NIR, p < 0.05). Additionally, neuronal death in the CA1/CA3 regions of the hippocampus, assessed by counting surviving neurons with stereology, was attenuated by treatment with NIR (17917 ± 5534 neurons/mm 3 CA/CPR vs. 44655 ± 5637 neurons/mm 3 CA/CPR + NIR, p < 0.05). All data is reported as mean ± SEM. Conclusions: These data provide evidence that noninvasive modulation of mitochondria, achieved by transcranial irradiation of the brain with NIR, mitigates post-cardiac arrest brain injury.

Routine Left Ventricular Pacing for Patients Undergoing Transcatheter Aortic Valve Replacement

ABSTRACT Background : Rapid ventricular pacing is often required during transcatheter aortic valve replacement (TAVR) procedures. Pacing via the retrograde left ventricular guidewire (LV-GW) is an alternative strategy to conventional pacing using a right ventricular temporary pacing wire (RV-TPW). We report our single center experience with this strategy. Methods : Two-hundred twenty-six patients who underwent transfemoral TAVR using pacing via LV-GW were included in this retrospective observational study. Results : LV-GW pacing was successful in 224 (99%) of the cases. In two (1%) patients, a RV-TPW was inserted after attempted LV-GW pacing because of stimulation failure (n = 1) or instability (n = 1). Procedural TAVR success was obtained in 94.7% of the cases. Procedural complication rate was low and included 2.7% vascular complications, 0.9% unsuccessful valve deployment and 3.1% in-hospital death. Pericardial effusion requiring intervention occurred in three (1.3%) cases and was related to LV perforation (0.9%) and annular rupture (0.4%). As expected, no case of RV perforation was observed. Conclusions : Pacing using LV-GW is a valuable alternative to RV-TPW for TAVR procedures. This avoids the need for an RV-TPW placement and reduces the risk of cardiac tamponade from RV perforation.

Insights into the Development of a Life-Sustaining Orthotopic Cardiac Xenotransplant Model

Introduction Advances in clinical immunosuppression and characterization of optimal donor genetics continue to move the field of xenotransplantation toward a clinical reality. Cardiac xenograft survival in a non-life supporting heterotopic model has been extended to greater than 900 days as previously described by our lab. Orthotopic life supporting models for cardiac xenografts are being developed with the major barrier being significant peri-operative mortality. We detail the development of an orthotopic pig-to-baboon cardiac xenotransplant model, offering insights gained over time for replication of the model. Materials and Methods Specific pathogen free baboons were transplanted with GTKO.CD46 donor pig hearts in the orthotopic position (n = 3) by cardiac transplant and congenital cardiac surgeons. The clinical team also included a perfusionist and cardiac anesthesiologist. Detailed reports were generated regarding equipment and medications required for the cases to approximate clinical orthotopic cardiac transplantation. Monitoring capabilities were optimized as well as resuscitative access and strategy. These baboons were recovered from prior experiments and per institutional protocol were approved for non-survival studies; cases were performed with intended short term survival under anesthesia followed by elective euthanasia. Results and Discussion All recipient baboons were transplanted and weaned off of cardiopulmonary bypass with life sustaining cardiac function. Low dose inotropic support was continued in all cases; vasopressor support was continued in one case. Two cases were electively terminated after wean from bypass; one recipient suffered arrest three hours post wean from bypass. Recipients were monitored using femoral arterial lines, transesophageal echocardiogram, external EKG, continuous pulse oximetry, and serial bloodwork including ABG, CBC, BMP, and ACT. Central venous access with multiple lumens was critical to post-operative care. Invasive hemodynamic monitoring, pretreatment with anti-arrhythmics, and availability of cardioversion for the donor pig allowed rapid reversal of fibrillation episodes during procurement. Ideal cold ischemia time was found to be close to one hour; shorter ischemia time resulted in poorer xenograft function (n = 1) as evidenced by difficult wean from bypass and persistent need for vasopressor support. Atrial and ventricular pacing wires proved integral to the cardiopulmonary bypass weaning process. Conclusion Cardiac xenotransplantation is a potential solution to the paucity of human organs. Technical refinement of the life-supporting orthotopic cardiac xenotransplant with expert clinical help and applying human standards of post-operative care are the critical next step toward a clinical reality. Here we detail our experience developing an operative and critical care approach to the orthotopic cardiac xenotransplantation model.

Quadruple Valve Replacement for Carcinoid Heart Disease.

IntroductionCarcinoid heart disease most frequently involves the tricuspid or, more rarely, the pulmonary valve and presents with right heart failure as 5-HT is metabolized by the lung. Left-sided valve involvement is quite rare. We describe our experience of 3 patients presenting with heart failure secondary to carcinoid heart disease affecting all four cardiac valves. There are only four previous isolated case reports in the literature.MethodsAll three patients underwent quadruple valve replacement during a single operation. Right ventricular outflow tract reconstruction with a pericardial patch was performed in all patients. For 24 hours prior to surgery, all patients received intravenous octreotide, which continued in intensive care for at least 24 hours.ResultsMean cross-clamp and bypass times were 175 (range 164-197 minutes) and 210 (range 195-229 minutes) minutes, respectively. Mean intensive treatment unit (ITU) and inpatient stays were 2.3 (range 2-3 days) and 12 (range 9-16 days) days, respectively. One patient was reopened for bleeding 4 hours postoperatively from a ventricular pacing wire site. None required a permanent pacemaker postoperatively. There were no other complications in any patient. The quality of life was excellent at 6-16 months clinic follow-up as they were in NYHA 1. Postoperative echocardiography showed no paravalvular leaks and well-functioning prostheses in all cases.ConclusionSurgery to replace all four valves is feasible with excellent medium-term survival and a very low rate of complications. Patients with carcinoid heart disease should always be considered for surgery irrespective of the extent of valvular involvement.

Surgical Treatment of Anomalous Aortic Origin of Coronary Arteries: The Reimplantation Technique and Its Modifications

Although anomalous aortic origin of a coronary artery has been described as a benign anomaly in the past, several reports suggest that such an anomaly may be the cause of sudden death in children and younger adults. Increased cardiac output during exercise may result in compression of the anomalous coronary artery when it runs between the aorta and the pulmonary artery or when its aortic origin is narrowed and its proximal course is intramural. It is unlikely that this rare anomaly would be identified during infancy, but once diagnosis has been made, indication to proceed with surgery is controversial. Nevertheless, if surgery is recommended, several operative techniques may be used, depending on the specific anatomy; unroofing, direct reimplantation, patch enlargement, and even coronary artery bypass grafting have been proposed. In this short report, we focus on different techniques of coronary reimplantation. As we already know from the arterial switch operation in neonates and from aortic root repair or replacement in adults, sufficient mobilization is necessary to allow direct reimplantation in the correct sinus to avoid kinking and other distortion.

The Utility of Atrioventricular Pacing via Pulmonary Artery Catheter During Transcatheter Aortic Valve Replacement

HE DEVELOPMENT OF TRANSCATHETER aortic valve replacement (TAVR) has led to the treatment of calcific aortic stenosis in patients whose condition might otherwise be considered inoperable if relegated to traditional aortic valve surgery. Although the ability to replace a patient’s aortic valve in this manner represents an important advancement in the treatment of aortic valve disease, there remain many challenges associated with successfully performing the procedure. One of these challenges is the ability to maintain hemodynamic stability during valve positioning and then recover stability after its deployment. Several factors can complicate this mission. The most obvious relate to the patient’s underlying aortic valve pathology as well as other concomitant cardiac disease. During valve positioning, the interposition of the deployment system across an already compromised aortic valve will further limit the native valve’s effective orifice area and also can promote regurgitation. Mechanical or functional mitral regurgitation also may occur during this process, producing additional strain on the myocardium. The cardiovascular system is further burdened by the need for cardiac “stand-still” during valve deployment. This is achieved by inducing rapid ventricular pacing (V-pacing). Hemodynamic recovery after this may be difficult, particularly if the pacing runs are protracted or successive. Delayed recovery can promote further myocardial ischemia, initiating a downward spiral that may prove intractable without significant intervention, including the need for mechanical circulatory support. Management can be complicated further by the development of conduction abnormalities (CA) after TAVR. This association has been well documented, but most of the literature has discussed them in regard to postoperative management, particularly the potential need for permanent pacemaker (PPM) placement. 1–4 However, CAs typically present during or immediately after valve deployment 5 and their acute hemodynamic effects have, in contrast, largely been ignored in published reports. This may be an important omission because the acute loss of atrioventricular (AV) synchrony may be tolerated poorly given the common association of ventricular hypertrophy and diastolic dysfunction in patients with aortic stenosis. In addition, because of the percutaneous nature of the procedure there are limited intraoperative rhythm management options available should the CA be associated with hemodynamic instability. Because of these concerns, all patients undergoing TAVR at this institution have percutaneous right atrial (RA) and right ventricular (RV) endocardial pacing wires placed via a specialized pulmonary artery catheter (PAC), unless they already have a PPM or have pre-existing atrial fibrillation (Fig 1). What follows is the discussion of a case that exemplifies the important benefits of this technique. CASE A 91-year-old woman with progressive dyspnea on exertion secondary to critical aortic stenosis presented for TAVR. The patient’s medical history also was significant for coronary artery disease with drug-eluting stents placed 2 years earlier, non–insulin-dependent diabetes mellitus, and temporal arteritis. Preoperative echocardiography revealed normal left ventricular function but with severe concentric hypertrophy, moderate mitral valve stenosis and regurgitation, and moderate-to-severe tricuspid regurgitation. The baseline electrocardiogram (ECG) was notable for sinus rhythm at 76 beats/min with an incomplete right bundle-branch block (RBBB) and a PR interval of 156 ms. A transaortic surgical approach was chosen because of the presence of a small and tortuous aorta with significant atheroma as well as the patient’s small body size, the combination of which limited both transapical and transfemoral deployment. After the induction of general anesthesia, a thermodilution PAC with two additional ports allowing the introduction of endocardial pacing wires into both the RA and RV (A-V Paceport Catheter, Edwards Lifesciences Corp., Irvine, CA) was inserted through a 9- French introducer sheath that had been placed into the right internal jugular vein (IJV). In order to properly position the pacing wires, the PAC was advanced while the pressure waveforms of both the catheter tip and the RV Paceport orifice were simultaneously monitored. Once the catheter tip entered the pulmonary artery (PA), it was further advanced until an RV pressure waveform was seen from the RV Paceport orifice, which indicated that this port had crossed the tricuspid

Cardiac Resynchronization Therapy Using a Dual Chamber Pacemaker in Patients with Severe Left Ventricular Dysfunction and a Left Bundle Branch Block

Through the use of a dual chamber (DDD) pacemaker, we achieved a cardiac resynchronization effect in a 51-year-old female patient who was transferred to our hospital from another hospital for an operation for three-vessel coronary artery disease. Her electrocardiogram showed a left bundle branch block (LBBB) and a prolonged QRS interval of 166 milliseconds. Severe left ventricle (LV) dysfunction was diagnosed via echocardiography. Coronary artery bypass grafting (CABG) was then performed. In order to accelerate left atrial activation and reduce the conduction defect, DDD pacing using right atrial and left and right ventricular pacing wires was initiated postoperatively. The cardiac output was measured immediately, and one and twelve hours after arrival in the intensive care unit. The cardiac output changed from 2.8, 2.4, and 3.6 L/min without pacing to 3.5, 3.4, and 3.5 L/min on initiation of pacing. The biventricular synchronization using DDD pacing was turned off 18 hours after surgery. She was transferred to a general ward with a cardiac output of 3.9 L/min. In patients with coronary artery disease, severe LV dysfunction, and LBBB, cardiac resynchronization therapy can be achieved through DDD pacing after CABG.

Is it worth placing ventricular pacing wires in all patients post-coronary artery bypass grafting?

A best evidence topic in cardiac surgery was written according to a structured protocol. The question addressed was whether ventricular pacing wires should be placed routinely in all patients undergoing coronary artery bypass grafting (CABG) regardless of immediate post-cardiopulmonary bypass (CPB) rhythm status. Using the reported search, 142 papers were found, from which 10 papers represented the best evidence on the subject. The author, date and country of 10 publications, study type, patient group studied, relevant outcomes and results are tabulated. Complete atrio-ventricular (AV) block is the main reason for inserting ventricular pacing wires upon conclusion of CABG. Eight studies found complete AV block to be a rare entity post-CABG. The rate of complete AV block in CABG in our review ranged from 0.3 to 24%. The calculated average rate of AV block in all studies was 2.4%. The number needed to treat with ventricular wires to support a patient who develops AV block is 42. One randomized controlled trial found 3% risk of complete AV block post-CABG. Another cohort of 222 patients revealed a rate of 1.8% for complete AV block. For one cohort of 770 patients, post-CABG the rate of complete AV block was found to be 0.3%. In one cohort of 25 patients, there was a rate of 4% for complete AV block post-CABG. Another study of 564 patients revealed a rate of 0.7% for complete AV block. A study of 4999 patients post-CABG reported a rate of 1.2% for complete AV block. In one cohort of 93 patients, there was a 4% risk of complete AV block. Another cohort of 62 patients showed a rate of 1.6% for complete AV block. Only two papers found the rate of complete AV block post-CABG to be as high as 24 and 16%. Both studies were limited by sample size. In conclusion, routine ventricular pacing wire insertion post-CABG is unnecessary given that routine use of ventricular wires can occasionally cause complications such as bleeding and cardiac tamponade and thus is not risk free. We also found that the incidence of complete AV block is probably higher in on-CPB CABG than off-CPB CABG and that AV pacing may be haemodynamically beneficial for some patients postoperatively.

Colonic Injury From Temporary Epicardial Pacing Wires

A 72-year-old man who had undergone a three-vessel coronary artery bypass grafting, aortic valve replacement, and tricuspid valve repair became comatose 1 week after the procedure. Signs of intraabdominal sepsis developed 6 days later, leading to laparotomy on his 12th postoperative day. The Intraoperative finding was a perforating injury to the transverse colon caused by the ventricular temporary pacing wires. A defunctioning double-barreled transverse colostomy was performed, after which the patient started to recover. He was discharged home 2 weeks later.

Fortuitous Vasculitis

A 43-year-old man with a cardiac device for dilated cardiomyopathy presented with fever, night sweats, and weight loss. Investigations revealed pancytopenia, acute renal failure, abnormal lung function, and raised inflammatory markers. A renal biopsy demonstrated pauci-immune necrotizing crescentic glomerulonephritis. He was diagnosed with pulmonary–renal antineutrophil cytoplasmic antibody-negative systemic small vessel vasculitis. He commenced immunosuppression with prednisolone and cyclophosphamide with recovery from pancytopenia and improvement in renal function 3 months later. Subsequently, a bone marrow culture grew Mycobacterium fortuitum. Isolation on repeat peripheral mycobacterial blood cultures prompted treatment with ciprofloxacin and clarithromycin. Four months later, he presented with neutropenic sepsis, influenza A/H1N1, and Aspergillus flavus pneumonia. Despite treatment he deteriorated. A transthoracic echocardiogram revealed a vegetation on the right ventricular pacing wire. The device was removed. The vegetation revealed acid and alcohol fast bacilli on Ziehl–Neelsen staining and grew M. fortuitum on culture, sensitive to ciprofloxacin and clarithromycin. Despite device removal and antimicrobial therapy, the patient succumbed to treatment-related complications. The association between glomerulonephritis and endocarditis is well known; however, this is the first case to our knowledge describing pauci-immune necrotizing crescentic glomerulonephritis in the context of M. fortuitum endocarditis. Clinicians should maintain a high index of suspicion for endocarditis in patients with a cardiac device who present with fever and pauci-immune necrotizing crescentic glomerulonephritis. Patients should be investigated with mycobacterial blood cultures, at least three sets of standard blood cultures and transthoracic and transesophageal echocardiography. Clinicians should beware the perils of immunosuppression in the face of an occult sepsis.

Migration of retained right ventricular epicardial pacing wire into the pulmonary artery: A rare complication after heart surgery

Migration of retained right ventricular epicardial pacing wire into the pulmonary artery: A rare complication after heart surgery

Cardiac Autotransplantation

Cardiac Autotransplantation

Acute Hemodynamic Effects of Cardiac Resynchronization Therapy in Patients with Poor Left Ventricular Function During Cardiac Surgery

Cardiac resynchronization therapy improves systolic function in patients with heart failure and left ventricular (LV) dyssynchrony. However, the effect of biventricular (BiV) pacing on perioperative hemodynamics in cardiac surgery is not well known. We investigated the acute hemodynamic response using LVdP/dt(max) in patients with depressed LV function and conduction disturbances undergoing cardiac surgery. Patients with LV ejection fraction of < or =35%, QRS duration of >130 ms, and left bundle branch block undergoing aortocoronary bypass and valve surgery were included. Temporary atrial and left and right ventricular pacing wires were applied, and LVdP/dt(max) was measured with a high fidelity pressure wire in the left ventricle at the end of cardiopulmonary bypass. Responders had a > or =10% increase in LVdP/dt(max). Eleven patients (age 63 +/- 11 years, eight males) with a LV ejection fraction 0.29 +/- 0.06% were included. Compared with right ventricular pacing (782 +/- 153 mmHg/sec), there was a significant improvement in the mean LVdP/dt(max) during simultaneous BiV pacing (849 +/- 174 mmHg/sec; p = 0.034) and sequential BiV pacing with the LV 40 ms advanced (880 +/- 157 mmHg/sec; p = 0.003). Improvement during LV pacing alone was not significant (811 +/- 141 mmHg/sec). Six patients were responders with simultaneous and nine with sequential BiV pacing. Only sequential BiV pacing had a significant improvement in LV systolic pressure (p = 0.02). BiV pacing results in acute hemodynamic improvement of LV function during cardiac surgery. Optimization of the interventricular pacing interval contributes to the effect of the therapy.

One-Stage Repair of Extensive Thoracic Aortic Aneurysm Using the Arch-First Technique and Bilateral Anterior Thoracotomy

One-Stage Repair of Extensive Thoracic Aortic Aneurysm Using the Arch-First Technique and Bilateral Anterior Thoracotomy

Repair of Tetralogy of Fallot with Absent Pulmonary Valve Syndrome

Tetralogy of Fallot (TOF) with absent pulmonary valve syndrome (APVS) occurs in 5% of patients with TOF. TOF-APVS includes an anterior malalignment ventricular septal defect (VSD) similar to TOF with pulmonary stenosis. The right ventricle is hypertrophied and may contain obstructing muscle bands in addition to infundibular narrowing. The pulmonary annulus is mildly to moderately hypoplastic with vestigial nubbins of nonfunctional myxomatous tissue rather than developed valve leaflets. The size of the main pulmonary artery ranges from normal to aneurysmal depending on the severity of the anomaly, whereas the branch pulmonary arteries are markedly aneurysmal, often two to three times their normal diameters. The hilar portions of the pulmonary arteries may also be dilated. The segmental branches are of normal size and appear as multiple orifices arising from the dilated portion of the artery when viewed from inside the vessel. A patent ductus arteriosus is never present in TOF-APVS. The combination of a VSD, pulmonary insufficiency, and a patent ductus arteriosus would potentially produce physiologic aortic insufficiency: left ventricular output could flow retrograde through the ductus, into the right ventricle, across theVSD,andbackintotheleftventricle.Ithasbeenproposed that the absence of a pulmonary valve influences premature closure of the ductus, or the fetus would not survive. The highly pulsatile flow through the pulmonary arteries may result in the aneurysmal dilation. 1,2 Patients with TOF-APVS can be divided into two groups. The first group presents in the neonatal period with respiratory distress, attributed to compression of the tracheobronchial tree by the aneurysmal pulmonary arteries. These patients require early surgery to avoid morbidity and death from respiratory distress and heart failure. The second group of patients is less symptomatic in infancy and may be identified later in life with symptoms of congestive heart failure, or classic TOF cyanotic spells. These patients can be managed similarly to other patients with TOF and undergo elective repair. There are two major debated issues regarding the surgical management of neonates with TOF-APVS: management of the aneurysmal pulmonary arteries, and placement of a pulmonary valve in the right ventricular outflow tract. Multiple operations have been proposed to address these issues. 3-10 In the operation we describe below, we remove the maximal amount of abnormal pulmonary arterial tissue and place a right ventricular to pulmonary artery homograft conduit. Complete excision of the main and branch pulmonary arteriesremovesalmostallaneurysmaltissue,therebyminimizing any chance of persistent tracheobronchial compression. Use of a homograft places a valve in the pulmonary outflow tract, which simplifies the postoperative management of pulmonary hypertension.

Adverse effects of atrioventricular synchronous right ventricular pacing on left ventricular sympathetic activity, efficiency, and hemodynamic status

Right ventricular (RV) pacing is now recognized to play a role in the development of heart failure in patients with and without underlying left ventricular (LV) dysfunction. We used the cardiac norepinephrine spillover method to test the hypothesis that RV pacing is associated with cardiac sympathetic activation. We studied 8 patients with normal LV function using temporary right atrial and ventricular pacing wires. All measurements were carried out during a fixed atrial pacing rate. The radiotracer norepinephrine spillover technique was employed to measure total body and cardiac sympathetic activity while changes in LV performance were evaluated with a high-fidelity manometer catheter. Atrioventricular synchronous RV pacing, compared with atrial pacing alone, was associated with a 65% increase in cardiac norepinephrine spillover, an increase in LV end-diastolic pressure, and a reduction in myocardial efficiency. These responses may play a role in the development of heart failure and poor outcomes that are associated with chronic RV pacing.

An unusual twist: ventricular tachycardia induced by a loop in a right ventricular pacing wire

Sir, An 80-year-old lady presented to our Accident and Emergency department with episodes of recurrent syncope that were preceded by shortness of breath, but no chest pain or palpitations. She had a past history of ischaemic heart disease and complete heart block, for which a dual-chamber pacemaker had been inserted 4 months previously. All the episodes of syncope had occurred following pacemaker implantation, and a Holter monitor had been fitted to investigate them. On examination, her heart rate was 70 bpm and regular. She exhibited signs of heart failure; jugular venous pressure was raised and bilateral crepitations were heard at the lung bases. Chest X-ray confirmed pulmonary oedema …

Participation of the Atrial Components of a Dual-Chamber Cardiac Pacemaker During Ventricular Pacing

A 70-year-old man with coronary artery disease, chronic atrial firillation, and cardiomegaly was scheduled for redo coronary bypass urgery. His initial heart rate was 38 beats/min. Because of the bradyardia and the epicardial scarring expected from the previous surgery, pacing probe was made ready in the right ventricular channel of a aceport pulmonary artery catheter (Edwards Lifesciences, Irvine, CA) nserted via the right internal jugular vein.4,5 After surgical revascularzation (performed with cardiopulmonary bypass and hypothermic poassium cardioplegia), the patient underwent electrical defibrillation, hich restored sinus rhythm with first-degree atrioventricular block. he surgeon attached pairs of epicardial pacing wires to the right trium and the right ventricle. After chest closure, the patient’s rhythm everted to atrial fibrillation. Subsequently, the thresholds for the epiardial ventricular pacing wires increased and then failed to capture at he maximal output (25 mA) of the temporary pacemaker (Medtronic 388, Minneapolis, MN). The endocardial ventricular pacing probe was dvanced 4 cm from its channel, and transvenous pacing was successully instituted with the Medtronic 5388 pacemaker programmed to eliver 15 mA ventricular pulses at 80 beats/min in the demand mode VVI). Interestingly, both demand (VVI) and asynchronous (VOO) transenous ventricular pacing failed whenever the epicardial atrial wires ere detached from the pulse generator. Even though the atrial ortion of the dual-chamber pacer was turned “off,” the atrial ystem participated in ventricular pacing (Fig 1). The circuit is iagrammed in Figure 2. The epicardial atrial wires were no longer required for ventricular acing when the endocardial ventricular pacing probe was advanced to rotrude 6 cm, instead of 4 cm, from the Paceport catheter. The aceport probe is comprised of 2 wires, one of which projects farther han the other. Advancing the probe enabled both wires to make contact ith the right ventricular endocardium. With both Paceport wires in ontact with the right ventricular endocardium, attached atrial wires ere not required for ventricular pacing. However, when only the distal ire of the Paceport probe made contact with the ventricular endocarium, then an effective ventricular pacing circuit was completed by eans of the epicardial atrial wires and the atrial portion of the ual-chamber pacer. By means of an oscilloscope (Tektronix digital model 2430, Beaerton, OR), this unconventional pacing possibility was duplicated in he laboratory. A 500-ohm resistor was run from the V pole of the ulse generator to either the V pole or the A pole. The pacemaker as set to deliver 15 mA pulses at 80/min in the VVI mode, and the otential difference across the resistor was tracked in time. Four edtronic 5388 pacemakers were examined. As expected, the V V rrangement produced strong electrical pulses. The amplitudes were .62 0.12 V, and the widths were 1.52 0.02 milliseconds. Howver, the V A arrangement also produced significant pulses (0.58 .04 V and 1.51 0.04 milliseconds). Significant pulses were also etected in a V A arrangement at higher amperage, but significant ulses were not detected in V A or in V A situations. p

INVITED COMMENTARY

Placement of temporary atrial and ventricular pacing wires after cardiac surgery continues to be the standard of care. The ideal temporary pacing wire must sense and pace reliably throughout the postoperative period, both in the atrial and ventricular positions, be easily placed and removed, and without significant risk of complications or discomfort to the patient. As none of the currently used temporary pacing wires have been found to be clearly superior to another, most cardiac surgeons use wires and insertion methods they are comfortable with and have found to be reliable.

Epicardial atrial defibrillation: successful treatment of postoperative atrial fibrillation

Background Atrial fibrillation is the most common complication after cardiac surgery. Current medical treatment using antiarrhythmics and anticoagulants has a significant morbidity. The goal of this study was to determine if epicardial atrial defibrillation can be safely performed and return patients to sinus rhythm. Methods A prospective analysis of patients undergoing cardiac surgery was performed. Patients with a prior pacemaker/defibrillator, history of arrhythmia, preoperative antiarrhythmic, age greater than 85 years, history of stroke, or intraaortic balloon pump were excluded. Temporary epicardial atrial cardioversion wires were placed on the right and left atrium. Bipolar atrial and ventricular pacing wires were also placed. The wires were tested in the operating room. Patients who went into postoperative arial fibrillation were cardioverted with 3 J, 6 J, or 9 J. Results There were 45 patients enrolled. Sixteen patients (35%) went into postoperative arial fibrillation during their hospital stay. Mean time to onset of arial fibrillation was 2.6 ± 1.4 days after surgery. Fifteen patients were successfully cardioverted to sinus rhythm on the primary cardioversion, with mean of 5.7 ± 2.4 J. One patient was cardioverted at 6 hours after onset of arial fibrillation, at 6 J. Recurrent arial fibrillation occurred in 4 patients during their hospital stay. All 4 of these patients were cardioverted with a mean of 6.4 ± 2.6 J. All wires were removed the day before patients were discharged. There were no complications with wire insertion or removal. There were no adverse neurologic events. The mean hospital stay was 5.1 ± 2.2 days. All patients were in sinus rhythm at 1 month follow-up. Conclusions The use of a temporary atrial defibrillator to resynchronize patients in postoperative arial fibrillation is safe and effective.