David C. Kress

Purely internal thoracic artery grafts: outcomes

BACKGROUND Most of our patients with coronary artery disease have undergone bypass exclusively with purely internal thoracic artery grafts (PITA). Our goal has been to lengthen the time a patient benefits from coronary bypass operations. The present report describes an 8.5-year study of outcomes including mortality and the need for reintervention in patients who have undergone bypass with PITA. METHODS We studied 897 patients who underwent PITA with a total of 3,784 internal thoracic artery (ITA) grafts (4.2 grafts per patient). Connecting ITA to ITA along with sequential anastomosis made the procedure possible. RESULTS Early mortality for the group was 2.3%. Freedom from death was 86% and freedom from reintervention was 94% at 5 years after the operation. CONCLUSIONS The acceptable early and late mortality and the 94% freedom from reintervention as long as 8.5 years after operation in this group of patients inspire us to continue choosing PITA for patients with three-vessel coronary artery disease.

Validation of a left atrial lesion pattern for intraoperative ablation of atrial fibrillation

BACKGROUND Evidence that atrial fibrillation may begin in early stages from triggers or reentry circuits primarily in the left atrium suggests that the entire Maze 3 lesion pattern may be unnecessary. In the present study we describe a new left atrial lesion pattern for intraoperative linear ablation of chronic atrial fibrillation. METHODS Endocardial radiofrequency ablation was performed on 12 dogs with chronic atrial fibrillation. Lesions to isolate pulmonary veins in pairs, the left atrial appendage, and connecting lesions between these structures were administered in a randomized approach. RESULTS Twelve dogs were in chronic atrial fibrillation for 31 +/- 21 days before ablation. Atrial fibrillation was successfully ablated and rendered noninducible in all 12 dogs. All treatment failures observed with less than the full lesion pattern became a success when the remaining lesions were given. CONCLUSIONS Atrial fibrillation ablation using this left atrial lesion pattern is highly successful in this model. This approach may have significant utility as a concomitant procedure for patients with atrial fibrillation undergoing mitral valve procedures.

The CURE-AF trial: a prospective, multicenter trial of irrigated radiofrequency ablation for the treatment of persistent atrial fibrillation during concomitant cardiac surgery.

BACKGROUND Ablation technology has been introduced to replace the surgical incisions of the Cox-Maze procedure in order to simplify the operation. However, the efficacy of these ablation devices has not been prospectively evaluated. OBJECTIVE The purpose of this study was to examine the efficacy and safety of irrigated unipolar and bipolar radiofrequency ablation for the treatment of persistent and long-standing persistent atrial fibrillation (AF) during concomitant cardiac surgical procedures. METHODS Between May 2007 and July 2011, 150 consecutive patients were enrolled at 15 U.S. centers. Patients were followed for 6 to 9 months, at which time a 24-hour Holter recording and echocardiogram were obtained. Recurrent AF was defined as any atrial tachyarrhythmia (ATA) lasting over 30 seconds on the Holter monitor. The safety end-point was the percent of patients who suffered a major adverse event within 30 days of surgery. All patients underwent a biatrial Cox-Maze lesion set. RESULTS Operative mortality was 4%, and there were 4 (3%) 30-day major adverse events. Overall freedom from ATAs was 66%, with 53% of patients free from ATAs and also off antiarrhythmic drugs at 6 to 9 months. Increased left atrial diameter, shorter total ablation time, and an increasing number of concomitant procedures were associated with recurrent AF (P <.05). CONCLUSION Irrigated radiofrequency ablation for treatment of AF during cardiac surgery was associated with a low complication rate. No device-related complications occurred. The Cox-Maze lesion set was effective at restoring sinus rhythm and had higher success rates in patients with smaller left atrial diameters and longer ablation times.

Effect of cannulation site on the primary determinants of myocardial oxygen consumption during left heart bypass.

Various methods have been used to provide mechanical circulatory support for patients in cardiogenic shock following myocardial infarction or cardiac surgery. The most commonly used device currently is the intraaortic balloon pump (IABP) . Left ventricular (LV) bypass has also been used clinically, with devices varying from a simple roller pump to a gas-powered pulsatile left ventricular assist device. An important function of circulatory support devices is reduction of metabolic need to promote recovery of “stunned” myocardium. Studies on isolated cat papillary muscle show myocardial oxygen consumption (MV02) to be a function of developed tension and the velocity of shortening of the unloaded muscle [l]. Moreover, MVO2 has been shown to be directly proportional to LV wall stress in intact hearts [2]. LaPlace’s law states that T = PR/2, where T = wall stress in a sphere, P = transmural pressure, and R = radius. An LV assist device therefore should decrease wall stress and MV02 in proportion to its ability to decrease LV pressure and/or radius. Virtually all clinically proposed methods of LV bypass use left atrial-to-aortic rather than LV apical-to-aortic bypass, despite canine studies showing that LV cannulation provides more complete decompression of the heart than left atria1 cannulation [3]. It is unclear whether or not the technical ease of inserting an atria1 cannula is an adequate rationale for using left atrial-to-aortic bypass in patients with reversible LV dysfunction. The aim of this study is to determine the effect of cannulation site on myocardial oxygen consumption and on the three primary determinants of MV02 during left heart bypass: wall tension, contractile state, and heart rate. Previous studies which have compared the effect of cannulation site on MV02 used noninfarcted paced canine models. Canine hearts are small and collateral coronary flow is greater than in humans. To study MV02 in both the noninfarcted

Transition from cardiopulmonary bypass to the HeartMate left ventricular assist device

BACKGROUND Safe transition from cardiopulmonary bypass to the HeartMate left ventricular assist device without periods of low output, air emboli, or injury to the right ventricle is vital to its successful implantation. A right atrial-to-left ventricular shunt has been developed to purge quickly and completely all air from the system and prevent its reentry, as well as to assist the right ventricle during the transition from cardiopulmonary bypass to the HeartMate. METHODS From January 1994 through July 1996, we used an extracorporeal membrane oxygenation right atrial-to-left ventricular shunt during 17 HeartMate implantations in 16 patients. The shunt consists of the existing right atrial two-stage cannula, the bypass circuit, and a separate aortic line that fills the left ventricle using a 21F cannula in the lateral ventricular wall. Air is monitored in the heart and aorta using transesophageal echocardiography. RESULTS Ten of the 16 patients are living and 8 have undergone transplantation. Two patients are still using the device and are awaiting transplantation. None of the patients have experienced postoperative neurologic events suggestive of air emboli. CONCLUSIONS The extracorporeal membrane oxygenation right atrial-to-left ventricular shunt is simple and inexpensive to construct. It provides for a smoother and safer transition from cardiopulmonary bypass to the HeartMate left ventricular assist device.

Selective downregulation of mitochondrial electron transport chain activity and increased oxidative stress in human atrial fibrillation

Mitochondria are critical for maintaining normal cardiac function, and a deficit in mitochondrial energetics can lead to the development of the substrate that promotes atrial fibrillation (AF) and its progression. However, the link between mitochondrial dysfunction and AF in humans is still not fully defined. The aim of this study was to elucidate differences in the functional activity of mitochondrial oxidative phosphorylation (OXPHOS) complexes and oxidative stress in right atrial tissue from patients without (non-AF) and with AF (AF) who were undergoing open-heart surgery and were not significantly different for age, sex, major comorbidities, and medications. The overall functional activity of the electron transport chain (ETC), NADH:O2 oxidoreductase activity, was reduced by 30% in atrial tissue from AF compared with non-AF patients. This was predominantly due to a selective reduction in complex I (0.06 ± 0.007 vs. 0.09 ± 0.006 nmol·min(-1)·citrate synthase activity(-1), P = 0.02) and II (0.11 ± 0.012 vs. 0.16 ± 0.012 nmol·min(-1)·citrate synthase activity(-1), P = 0.003) functional activity in AF patients. Conversely, complex V activity was significantly increased in AF patients (0.21 ± 0.027 vs. 0.12 ± 0.01 nmol·min(-1)·citrate synthase activity(-1), P = 0.005). In addition, AF patients exhibited a higher oxidative stress with increased production of mitochondrial superoxide (73 ± 17 vs. 11 ± 2 arbitrary units, P = 0.03) and 4-hydroxynonenal level (77.64 ± 30.2 vs. 9.83 ± 2.83 ng·mg(-1) protein, P = 0.048). Our findings suggest that AF is associated with selective downregulation of ETC activity and increased oxidative stress that can contribute to the progression of the substrate for AF.

Pharmacological strategies for prevention of postoperative atrial fibrillation

Atrial fibrillation (AF) complicating cardiac surgery continues to be a major problem that increases the postoperative risk of stroke, myocardial infarction, heart failure and costs and can affect long-term survival. The incidence of AF after surgery has not significantly changed over the last two decades, despite improvement in medical and surgical techniques. The mechanism and pathophysiology underlying postoperative AF (PoAF) is incompletely understood and results from a combination of acute and chronic factors, superimposed on an underlying abnormal atrial substrate with increased interstitial fibrosis. Several anti-arrhythmic and non-anti-arrhythmic medications have been used for the prevention of PoAF, but the effectiveness of these strategies has been limited due to a poor understanding of the basis for the increased susceptibility of the atria to AF in the postoperative setting. In this review, we summarize the pathophysiology underlying the development of PoAF and evidence behind pharmacological approaches used for its prevention in the postoperative setting.

Circulating biomarkers predictive of postoperative atrial fibrillation

Postoperative atrial fibrillation (PoAF), a common complication of cardiac surgery, contributes significantly to morbidity, mortality, and increasing healthcare costs. Despite advances in surgical and medical management, the overall incidence of PoAF has not changed significantly, partly because of the limited understanding of mechanisms underlying acute surgery-related factors, such as myocardial injury, inflammation, sympathetic activation, and oxidative stress, which play an important role in the initiation of PoAF, whereas a preexisting atrial substrate appears to be more important in the maintenance of this dysrhythmia. Thus, in a majority of patients, PoAF becomes a manifestation of an underlying arrhythmogenic substrate that is unmasked after acute surgical stress. As such, the ability to identify which patients have this proarrhythmic substrate and are, therefore, at high risk for developing AF postoperatively, is important for the improved selection for prophylactic interventions, closer monitoring for complications, and establishing the probability of AF in the long term. This review highlights the role of the underlying substrate in promoting PoAF, proposed mechanisms, and the potential role of serum biomarkers to identify patients at risk for PoAF.

Left Atrial Laceration With Epicardial Ligation Device

Many new devices and techniques are being developed to attempt a reduction in embolic stroke risk for patients with atrial fibrillation who are either unable or unwilling to maintain long-term anticoagulation. One of these new devices (LARIAT®, SentreHEART Inc., Redwood City, California, USA) employs delivery of an epicardial suture to ligate the left atrial appendage after percutaneous pericardial and transseptal access. This series presents three clinical cases that demonstrate a serious and recurrent complication of left atrial laceration and cardiac tamponade shortly following delivery of an epicardial suture ligation to the left atrial appendage. Three clinical cases are described in detail with pre- and postprocedure angiography and echocardiography as well as illustrations reflecting the surgeons findings on direct visualization of the left atrial lacerations postligation. Potential hypotheses of each injury are examined in light of the case timelines and findings at sternotomy. There was no suggestion that tamponade was related to pericardial or transseptal access, but rather a complication with device delivery. These three patients quickly progressed to clinical cardiac tamponade despite attempted drainage, stressing the importance of cardiovascular surgery backup, including a cardiopulmonary bypass pump, when delivering novel, percutaneous ligation devices for the left atrial appendage.

Preoperative Depletion of C3 Improves the Survival of Guinea Pig-to-Rat Cardiac Xenograft Recipients

Rat strains with congenitally reduced total hemolytic complement activity do not reject cardiac xenografts hyperacutely. Prolongation of graft survival in the guinea pig-to-C6-deficient PVG rat donor/recipient combination has been observed. However, experience with this model has been complicated by a high postoperative mortality from respiratory distress. The authors hypothesized that placement of the xenograft resulted in local activation of complement, which contributed to remote pulmonary injury leading to respiratory dysfunction. To test this hypothesis, an attempt was made to reduce early complement component activation with the use of an antibody to rat C3 in C6-deficient PVG recipients. Six of eight untreated C6-deficient PVG recipients died in the immediate postoperative period with vigorously beating heart grafts, whereas only 2 of 14 C6-deficient recipients pretreated with anti-rat C3 antibody died within 24 h postoperatively. Although pretreatment with anti-C3 antibody improved survival of recipients, the duration of cardiac xenograft survival was similar whether the recipients were pretreated or not. The use of anti-C3 antibody in C6-deficient rats is a valid approach to studying xenotransplantation in the absence of hyperacute rejection and has an additional advantage in that it does not require the use of expensive reagents such as cobra venom factor.