Michael Worthington

Atrial remodeling in an ovine model of anthracycline-induced nonischemic cardiomyopathy: remodeling of the same sort.

Atrial Remodeling in Doxorubicin Cardiomyopathy. Introduction: All preclinical studies of atrial remodeling in heart failure (HF) have been confined to a single model of rapid ventricular pacing. To evaluate whether the atrial changes were specific to the model or represented an end result of HF, this study aimed to characterize atrial remodeling in an ovine model of doxorubicin‐induced cardiomyopathy.

Atrial protective effects of n-3 polyunsaturated fatty acids: A long-term study in ovine chronic heart failure

BACKGROUND It has been suggested that omega-3 polyunsaturated fatty acids (n-3 PUFAs) may prevent the development of atrial fibrillation (AF). OBJECTIVE The purpose of this study was to evaluate the impact of these agents on development of the AF substrate in heart failure (HF). METHODS In this study, HF was induced by intracoronary doxorubicin infusions. Twenty-one sheep [7 with n-3 PUFAs treated HF (HF-PUFA), 7 with olive oil-treated HF controls (HF-CTL), 7 controls (CTL)] were studied. Open chest electrophysiologic study was performed with assessment of biatrial effective refractory period (ERP) and conduction. Cardiac function was monitored by magnetic resonance imaging. Atrial n-3 PUFAs levels were quantified using chromatography. Structural analysis was also performed. RESULTS Atrial n-3 PUFAs levels were twofold to threefold higher in the HF-PUFA group. n-3 PUFAs prevented the development of HF-related left atrial enlargement (P = .001) but not left ventricular/atrial dysfunction. Atrial ERP was significantly lower in the HF-PUFA group (P <.001), but ERP heterogeneity was unchanged. In addition, n-3 PUFAs suppressed atrial conduction abnormalities seen in HF of prolonged P-wave duration (P = .01) and slowed (P <.001) and heterogeneous (P <.05) conduction. The duration of induced AF episodes in HF-PUFA was shorter (P = .02), although AF inducibility was unaltered (P = NS). A 20% reduction of atrial interstitial fibrosis was seen in the HF-PUFA group (P <.05). CONCLUSION In this ovine HF study, chronic n-3 PUFAs use protected against adverse atrial remodeling by preventing atrial enlargement, fibrosis, and conduction abnormalities leading to shorter AF episodes despite lower ERP.

Minimally Invasive Mitral Valve Procedures: The Current State

Since its early days, cardiac surgery has typically involved large incisions with complete access to the heart and the great vessels. After the popularization of the minimally invasive techniques in general surgery, cardiac surgeons began to experiment with minimal access techniques in the early 1990s. Although the goals of minimally invasive cardiac surgery (MICS) are fairly well established as decreased pain, shorter hospital stay, accelerated recuperation, improved cosmesis, and cost effectiveness, a strict definition of minimally invasive cardiac surgery has been more elusive. Minimally invasive cardiac surgery started with mitral valve procedures and then gradually expanded towards other valve procedures, coronary artery bypass grafting, and various types of simple congenital heart procedures. In this paper, the authors attempt to focus on the evolution, techniques, results, and the future perspective of minimally invasive mitral valve surgery (MIMVS).

Early results of minimally invasive mitral valve surgery: initial series in a public hospital in Australia

PurposeThis study analyzes the initial experience with minimally invasive mitral valve surgery through a right minithoracotomy in a public teaching hospital in Australia and evaluates early surgical outcomes.MethodsA retrospective review of patients who underwent minimally invasive mitral valve surgery between November 2006 and March 2009 was performed.ResultsA total of 60 patients included 47 (78%) patients who had mitral valve plasty and 13 (22%) who had mitral valve replacement. The mean age was 61 ± 15 years; 33 (55%) patients were male; and 6 (10%) had had previous cardiac operations. The mean cardiopulmonary bypass and aortic cross-clamp times were 140 ± 46 and 93 ± 35 min, respectively. All patients who underwent mitral valve plasty left the operation room with no more than trivial residual mitral regurgitation. There was no operative mortality. Reoperation for bleeding and stroke occurred in 2 patients each. The mean intensive care unit and hospital stays were 3.1 ± 5.8 and 10.6 ± 8.9 days, respectively. Among the 47 patients with mitral valve plasty, 46 (98%) had mild or less mitral regurgitation on transthoracic echocardiography at discharge. There was one late death. No reoperation for the mitral valve has been observed so far. An echocardiography report was obtained for 34 of the 47 who had had mitral valve plasty at 12.1 ± 7.9 months postoperatively, and 27 (79%) of them had mild or less mitral regurgitation.ConclusionMinimally invasive mitral valve surgery through a right minithoracotomy was safely performed with no early mortality.

Long Term Outcomes Following Freestyle Stentless Aortic Bioprosthesis Implantation: An Australian Experience.

BACKGROUND The Freestyle stentless bioprosthesis (FSB) has been demonstrated to be a durable prosthesis in the aortic position. We present data following Freestyle implantation for up to 10 years post-operatively and compare this with previously published results. METHODS A retrospective cohort analysis of 237 patients following FSB implantation occurred at five Australian hospitals. Follow-up data included clinical and echocardiographic outcomes. RESULTS The cohort was 81.4% male with age 63.2±13.0 years and was followed for a mean of 2.4±2.3 years (range 0-10.9 years, total 569 patient-years). The FSB was implanted as a full aortic root replacement in 87.8% patients. The 30-day all cause mortality was 4.2% (2.0% for elective surgery). Cumulative survival at one, five and 10 years was 91.7±1.9%, 82.8±3.8% and 56.5±10.5%, respectively. Freedom from re-intervention at one, five and 10 years was 99.5±0.5%, 91.6±3.7% and 72.3±10.5%, respectively. At latest echocardiographic review (mean 2.3±2.1 years post-operatively), 92.6% had trivial or no aortic regurgitation. Predictors of post-operative mortality included active endocarditis, acute aortic dissection and peripheral vascular disease. CONCLUSIONS We report acceptable short and long term outcomes following FSB implantation in a cohort of comparatively younger patients with thoracic aortic disease. The durability of this bioprosthesis in the younger population remains to be confirmed.

Prevention of Sternal Wound Infections by use of a Surgical Incision Management System: First Reported Australian Case Series.

BACKGROUND Sternal wound infections are considered a costly and potentially devastating consequence of the median sternotomy in cardiothoracic surgery. Surgical incision management employs the technique of applying a closed, negative pressure vacuum dressing to a closed wound. Several studies have demonstrated a reduction in sternal wound infections using this system. METHODS A retrospective audit of cases receiving surgical incision management demonstrated a statistically significant reduction in sternal wound infections against a predicted rate. RESULTS Of the 62 patients identified, only one was complicated by a sternal wound infection with the greatest reduction seen in the high-risk infection group. CONCLUSIONS Although smaller in size, the results compared well to trials conducted in larger European and US centres. Although not advocating surgical incision management for routine use, it should be considered on patients considered high-risk for sternal wound infection, such as diabetics, the elderly and the obese.

Endothelial Denudation of Isolated Human Internal Mammary ArterySegments

Background: Endothelial denudation is an important approach to evaluate the role of the endothelium in vascular reactivity studies. Although approaches to remove the endothelium are well established in animal models, these methods have proved difficult to effectively translate to remnants of human Internal Mammary Artery (IMA) obtained during coronary bypass. This study sought to identify the optimal technique for endothelial denudation of IMA while preserving vascular contractile responses. Methods: IMA segments were subject to endothelial denudation using one of the following techniques: (1) surface abrasion, rubbing with a stainless steel wire, (2) vasoconstriction abrasion or (3) shear abrasion via infusion of an effervescent solution. Following intervention, IMA segments were evaluated by: (1) histochemistry to quantify structural damage and endothelial cell abundance and (2) functional endothelium-dependent vasodilator response using vascular myography in an organ bath preparation. Results: Vasoconstriction abrasion removed endothelial cells and caused disruption of the internal elastic lamina, these vessels failed to respond to the vasoconstrictor Phenylephrine (PE) or the endothelium-dependent vasodilator A23187. Surface abrasion alone was incomplete in removing endothelial cells, vessel vasodilated partially when challenged with A23187 in the presence of PE. Shear abrasion removed endothelial cells most effectively, as these pre-constricted vessels did not relax to A23187 but demonstrated increased sensitivity to PE. Conclusions: In this controlled comparative study assessing both structural and functional endpoints of endothelial denudation techniques, we have demonstrated that shear abrasion by infusion of an effervescent solution is the optimal technique to remove the endothelium and preserve vascular function in human IMA.

Beating heart minimally invasive mitral valve surgery in patients with previous sternotomy: the operative technique and early outcomes

Objective Reoperative mitral valve surgery is increasingly required and can be associated with significant morbidity and mortality. The beating heart minimally invasive mitral valve surgery has a proposed benefit in avoiding the risks of repeat sternotomy, with reducing the need for adhesiolysis and cardioplegia reperfusion injury. We describe our experience with such a technique in patients with previous sternotomy. Methods A retrospective study was performed and all patients undergoing surgery of mitral valve through a right limited thoracotomy without application of an aortic cross-clamp (beating heart) as a redo cardiac surgery between January 2006 and January 2015 were included (n=25). Perioperative data as well as the operative technique are presented. Results Six patients (24%) had two previous sternotomies and one (4%) had three previous sternotomies. Mitral valve repair was performed in 11 patients (44%). No patient required conversion to median sternotomy. Inotropic support beyond 4 hours after operation was required in seven patients (28%). Ventilation time was less than 12 hours in 14 patients (56%) with another six patients (24%) extubated within 24 hours after surgery. Postoperative course was complicated with cerebrovascular accident in two patients (8%). In-hospital mortality was 4% (n=1). There was no 30-day mortality after discharge. Conclusions Reoperative mitral valve surgery can be safely performed through a limited right thoracotomy approach on a beating heart while on full cardiopulmonary bypass. The technique can be associated with potentially shorter operation, shorter cardiopulmonary bypass and a less complicated recovery.

Cardiopulmonary Bypass in Non-Cardiac Surgery

BACKGROUND Cardiopulmonary bypass (CPB) and extracorporeal membrane oxygenation (ECMO) are used to facilitate circulatory support in standard cardiac surgery and emergency intervention, but CPB and ECMO are not used routinely in non-cardiac surgery involving the thorax and major vessels. The primary aim of this study was to identify the type of non-cardiac procedures and bypass used in our institution and review the patient outcomes including perioperative and bypass complications. METHODS A retrospective study was performed within the Royal Adelaide Hospital Cardiothoracic Surgery Unit (CTSU) that examined all operations between 2006 and 2014. There were 1,816 non-cardiac cases, of these nine used CPB or ECMO. Cases excluded from the study were those that required cardiac surgical management with the use of CPB or ECMO. RESULTS Twelve (12) non-cardiac surgery cases were reviewed, with three, and nine cases, respectively, using ECMO and CPB standby or support. The non-cardiac surgical procedures included eight thoracic cases, two renal cases and two tracheal cases. Of the thoracic cases, five were elective, two were bailout and one was an emergency. Both renal cases were bailout (with one as major vessel support and one as standby). Both tracheal cases were bailout (one as an emergency and one as standby). Intraoperative complications included severe haemorrhage in three cases. General postoperative complications included increased analgesia requirement, atelectasis, fever; and prolonged ECMO support and ICU stay which occurred in seven cases. No direct complications of CPB or ECMO are reported. Four of the 12 cases that encompassed thoracic, renal and tracheal surgery are discussed in detail. CONCLUSIONS Our review of 12 cases managed under the CTSU has shown that extracorporeal circulatory support can be used in a range of thoracic, renal and tracheal surgery. These surgical procedures have involved the management of haemodynamically unstable patients. Patient outcomes have been encouraging with few complications. With further research including the use of a larger sample size and control groups, more definitive conclusions could be made on the benefit of CPB and ECMO to patients in non-cardiac surgery.

Video-assisted thorascopic lobectomy for pulmonary arteriovenous malformations to prevent cerebral abscess: Images for Surgeons

A 58-year-old woman presented in 2007 with a left thalamic abscess. Seven pulmonary arteriovenous malformations (PAVM) within the left lower lobe were identified on computed tomography pulmonary angiography (CTPA). Prior to this episode, she had been asymptomatic. She met only one (visceral involvement) of the four clinical criteria for hereditary haemorrhagic telangiectasia (HHT), making the diagnosis ‘unlikely’. She additionally had no arteriovenous malformations identified in viscera other than lung. She was treated with antibiotics and stereotactic-guided aspiration of the cerebral abscess. Embolotherapy was performed with intravascular coiling to the three largest PAVM. In 2016, the patient re-presented with a right frontal abscess requiring stereotactic-guided right frontal craniotomy and resection. CTPA demonstrated recanalization of the previously coiled PAVM as well as multiple persisting PAVM confined to the left lower lobe (Fig. 1). Echocardiogram demonstrated an extra-cardiac shunt without evidence of valvular vegetations or a patent foramen ovale. Given the recurrence of PAVM and cerebral abscess following embolotherapy, and with PAVM confined to a single lobe, a surgical resection was considered to be the most definitive management option. Video-assisted thoracoscopic surgery (VATS) left lower lobectomy was performed. Intraoperatively, superficial PAVM on the surface of the lung were visualized in a serpiginous distribution reminiscent of Medusa’s head (Fig. 2). This illustrates what was described in the 1959 article by Bosher et al. Vascular anatomy at the lung hilar was normal. Standard left lower lobectomy was performed with division of the inferior pulmonary vein and en bloc division of the pulmonary artery and bronchus in the left lower lobe fissure. Histology of the resected specimen confirmed the diagnosis of PAVM (Fig. 3). Repeat echocardiography was performed three months post-operatively which demonstrated no evidence of a persisting extra-cardiac shunt. CTPA performed at 16 months postoperatively demonstrated no formation or recurrence of PAVM. PAVM are abnormal vessels in the pulmonary vasculature allowing communication between the arterial and venous circulation. PAVM are most commonly unilateral with a predilection for the lower lobes of the lung. Less than 15% of PAVM are bilaterally distributed. The vast majority of PAVM are associated with HHT or OslerWeber-Rendu syndrome, with greater than 90% of patients with PAVM confirmed to have ‘definite’ HHT as adjudged by the Curaςao diagnostic clinical criteria. Clinical diagnosis of HHT is determined by the presence of at least three of four criteria including epistaxes, telangiectasia, visceral lesions and/or family history.