Impact of COVID-19 on cardiac surgical training: Our experience in the United Kingdom.

The current evolving global pandemic caused by coronavirus disease-2019 (COVID-19) has dramatically impacted global health care systems, resulting in governments taking unprecedented measures to contain the spread of the infection, with adaptations by health care organizations. Research into understanding the pathophysiology behind this virus, to ascertain best medical management and treatment, has been accelerated to keep up with the rapidly evolving situation. There has been redeployment of medical and nursing staff to the frontlines and redistribution of health care resources. In addition, the cancellation of elective surgery and centralization of services to treat high-risk surgical cases will all, undeniably, have an impact on current surgical training with possible future implications. We aim to explore the impact COVID-19 is having on cardiac surgical training in the UK and what future implications this may have.

Surgical management of valve disease in the early 21st century.

Surgery offers good results for patients with significant valvular heart disease. Valve replacement and repair are the main surgical options. Older patients and redo procedures are increasingly frequent.

A retrospective analysis of myocardial preservation techniques during coronary artery bypass graft surgery: are we protecting the heart?

BACKGROUND: Retrograde perfusion into coronary sinus during coronary artery bypass graft (CABG) surgery reduces the need for cardioplegic interruptions and ensures the distribution of cardioplegia to stenosed vessel territories, therefore enhancing the delivery of cardioplegia to the subendocardium. Peri-operative myocardial injury (PMI), as measured by the rise of serum level of cardiac biomarkers, has been associated with short and long-term clinical outcomes. We conducted a retrospective analysis to investigate whether the combination of antegrade and retrograde techniques of cardioplegia delivery is associated with a reduced PMI than that observed with the traditional methods of myocardial preservation. METHODS: Fifty-four consecutive patients underwent CABG surgery using either antegrade cold blood cardioplegia (group 1, n = 28) or cross-clamp fibrillation (group 2, n = 16) or antegrade retrograde warm blood cardioplegia (group 3, n = 10). The study primary end-point was PMI, evaluated with total area under the curve (AUC) of high-sensitivity Troponin-T (hsTnT), measured pre-operatively and at 6, 12, 24, 48 and 72 hours post-surgery. Secondary endpoints were acute kidney injury (AKI) and inotrope scores, length of intensive care unit (ICU) and hospital stay, new onset atrial fibrillation (AF) and clinical outcomes at 6 weeks (death, non-fatal myocardial infarction, coronary artery revascularization, stroke). RESULTS: There was evidence that mean total AUC of hsTnT was different among the three groups (P = 0.050). In particular mean total AUC of hsTnT was significantly lower in group 3 compared to both group 1 (-16.55; 95% CI: -30.08, -3.01; P = 0.018) with slightly weaker evidence of a lower mean hsTnT in group 3 when compared to group 2 (-15.13; 95% CI -29.87, -0.39; P = 0.044). There was no evidence of a difference when comparing group 2 to group 1 (-1.42,; 95% CI: -12.95, 10.12, P = 0.806). CONCLUSIONS: Our retrospective analysis suggests that, compared to traditional methods of myocardial preservation, antegrade retrograde cardioplegia may reduce PMI in patients undergoing first time CABG surgery.

T1 mapping for myocardial extracellular volume measurement by CMR: bolus only versus primed infusion technique.

OBJECTIVES: The aim of this study was to determine the accuracy of the contrast "bolus only" T1 mapping cardiac magnetic resonance (CMR) technique for measuring myocardial extracellular volume fraction (ECV). BACKGROUND: Myocardial ECV can be measured with T1 mapping before and after contrast agent if the contrast agent distribution between blood/myocardium is at equilibrium. Equilibrium distribution can be achieved with a primed contrast infusion (equilibrium contrast-CMR [EQ-CMR]) or might be approximated by the dynamic equilibration achieved by delayed post-bolus measurement. This bolus only approach is highly attractive, but currently limited data support its use. We compared the bolus only technique with 2 independent standards: collagen volume fraction (CVF) from myocardial biopsy in aortic stenosis (AS); and the infusion technique in 5 representative conditions. METHODS: One hundred forty-seven subjects were studied: healthy volunteers (n = 50); hypertrophic cardiomyopathy (n = 25); severe AS (n = 22); amyloid (n = 20); and chronic myocardial infarction (n = 30). Bolus only (at 15 min) and infusion ECV measurements were performed and compared. In 18 subjects with severe AS the results were compared with histological CVF. RESULTS: The ECV by both techniques correlated with histological CVF (n = 18, r² = 0.69, p < 0.01 vs. r² = 0.71, p < 0.01, p = 0.42 for comparison). Across health and disease, there was strong correlation between the techniques (r² = 0.97). However, in diseases of high ECV (amyloid, hypertrophic cardiomyopathy late gadolinium enhancement, and infarction), Bland-Altman analysis indicates the bolus only technique has a consistent and increasing offset, giving a higher value for ECVs above 0.4 (mean difference ± limit of agreement for ECV <0.4 = -0.004 ± 0.037 vs. ECV >0.4 = 0.040 ± 0.075, p < 0.001). CONCLUSIONS: Bolus only, T1 mapping-derived ECV measurement is sufficient for ECV measurement across a range of cardiac diseases, and this approach is histologically validated in AS. However, when ECV is >0.4, the bolus only technique consistently measures ECV higher compared with infusion.

Aortic valve-sparing operations: dealing with the coronary artery that is too close to the aortic annulus.

During aortic root surgery, one of the coronary ostia is sometimes found to lie too close to one of the commissures to allow its safe detachment as a button while still preserving the native aortic valve. In the past, this has prevented aortic valve-sparing root replacement in cases of aortic root aneurysm. We describe a technique pertaining to the reimplantation method of aortic valve-sparing root replacement to deal with such a displaced coronary artery.

Outcomes of surgical intervention for isolated active mitral valve endocarditis.

OBJECTIVE: Although several studies have examined the outcomes of mitral valve repair for infective endocarditis, no studies have documented the long-term outcomes of surgical intervention for active endocarditis confined to the mitral valve. METHODS: One hundred four patients underwent surgical intervention for active infective endocarditis confined to the mitral valve over a 27-year period (mean age, 50 +/- 18 years; 52% female). The infected valve was native in 81 patients, previously repaired 6 patients, and prosthetic in 17 patients. Staphylococcus aureus was the most commonly isolated (32%) source of infection. Twenty-eight (27%) patients had annular abscesses. Surgical intervention consisted of valve repair or replacement for limited infection and radical resection, annular patch reconstruction, and valve replacement for annular abscess. Mean follow-up was 5.6 +/- 4.4 years (range, 0-20 years) and was complete. RESULTS: There were 9 (8.7%) in-hospital deaths and 28 (27%) late deaths. Overall survival at 5, 7, and 10 years was 73% +/- 5%, 68% +/- 5%, and 58% +/- 6%, respectively. At 7 years, freedom from recurrent endocarditis was 89% +/- 4% and freedom from reoperation was 94% +/- 3%. Event-free survival at 7 and 10 years was 60% +/- 6% and 46% +/- 7%, respectively, and was significantly higher in patients with native endocarditis versus those with nonnative endocarditis (ie, prosthetic or previously repaired; 7 years: 63% +/- 7% vs 50% +/- 12%, P < .005). Preoperative shock, S aureus infection, and bioprosthesis insertion were independent predictors of death from all causes. The patients in the bioprosthesis group were older (57 +/- 20 years vs 44 +/- 15 years in the mechanical group and 46 +/- 12 years in the repair group, P = .003). CONCLUSIONS: Surgical intervention for isolated active mitral valve endocarditis remains difficult, with high morbidity and mortality in the long term. Event-free survival is worse in those who have nonnative mitral valve endocarditis.

Outcomes of double valve surgery for active infective endocarditis.

OBJECTIVE: In active infective endocarditis the need for operating simultaneously on the aortic and mitral valves is frequent. There are no studies in the literature documenting long-term outcomes of double valve surgery for active endocarditis. METHODS: Ninety patients underwent double valve surgery for active endocarditis over a 26-year period (mean age, 53 +/- 16 years; 71% male patients). Prosthetic endocarditis was seen in 32 patients. Staphylococcus species was isolated in 29%. Forty-six (51%) patients had abscesses. Surgical intervention consisted of valve repair or replacement with limited infection or radical resection, patch reconstruction, and valve replacement for abscesses. Mean follow-up was 5.9 +/- 4.7 years (range, 0-18 years) and was complete. RESULTS: There were 14 (15.6%) in-hospital deaths and 29 (32.2%) late deaths. Overall survival at 5, 7, and 10 years was 68% +/- 5%, 59% +/- 6%, and 49% +/- 6%, respectively, and was reduced in those undergoing operations for prosthetic compared with native endocarditis (7-year survival, 39% +/- 9% vs 71% +/- 7%; P < .001). Freedom from recurrent endocarditis was 84% +/- 5% at 10 years. Freedom from reoperation was 91% +/- 4% at 10 years. Event-free survival at 7 and 10 years was 60% +/- 6% and 47% +/- 7%, respectively. No difference was observed between the native and prosthetic groups for recurrent endocarditis, late reoperation, or event-free survival. Prosthetic endocarditis, increasing age, preoperative shock, and diabetes mellitus were independent predictors of death from all causes. CONCLUSIONS: Double valve surgery for active endocarditis remains technically challenging and associated with significant morbidity and mortality perioperatively and in the longer term. Outcomes are worse in those who have prosthetic valve endocarditis.

Right ventricular hypertrophy with early dysfunction: A proteomics study in a neonatal model.

OBJECTIVE: Right ventricular hypertrophy and subsequent dysfunction is common in patients with congenital heart defects, but the molecular mechanisms underlying change from adaptive hypertrophy to dysfunction remain elusive. We used the novel technique of proteomics to characterize protein changes in right ventricular myocardium in a neonatal model of right ventricular hypertrophy and early dysfunction. METHODS: Twelve neonatal piglets were equally randomized to pulmonary artery banding (PAB group), or sham operation (thoracotomy without banding). After 4 weeks, right ventricular morphology and function were assessed in vivo using magnetic resonance imaging. Animals were humanely killed. Proteomics of right ventricular myocardium was performed. Purified right ventricular proteins were separated by 2-dimensional difference gel electrophoresis using fluorescent cyanine dyes. After gel imaging, software analysis revealed protein spots differentially expressed between the 2 groups; these spots were excised and identified by mass spectrometry. RESULTS: On magnetic resonance imaging, animals with pulmonary artery banding demonstrated significant right ventricular hypertrophy, cavity dilatation, and mild systolic impairment (right ventricular ejection fraction 39.8% +/- 15% vs 56.7% +/- 10% controls; P < .05). Right ventricular free wall mass on harvest confirmed right ventricular hypertrophy. Proteomic analysis revealed 18 proteins that were significantly differentially expressed: 5 structural proteins, 6 metabolic enzymes, 2 stress proteins, and 5 miscellaneous proteins. Expression of calsarcin-1 and vinculin was increased, as were certain metabolic enzymes, although F(1)-ATPase beta-chain and heat shock protein 70 decreased. CONCLUSIONS: This is the first study characterizing right ventricular protein changes in a large animal model specifically capturing the change from compensated to maladaptive hypertrophy. These findings can guide future work at elucidating the mechanisms in the pathophysiology of neonatal right ventricular hypertrophy and dysfunction.

Proteomics of cerebral injury in a neonatal model of cardiopulmonary bypass with deep hypothermic circulatory arrest.

OBJECTIVE: Concern over neurologic injury limits safe duration of deep hypothermic circulatory arrest (DHCA) in surgery for congenital cardiac disease. Proteomics is a novel and powerful technique to study global protein changes in a given protein system. Using a neonatal model of cardiopulmonary bypass with DHCA, we sought to characterize the protein changes associated with DHCA brain injury. METHODS: Ten neonatal piglets were randomized to cardiopulmonary bypass with DHCA or sham operation. DHCA animals underwent induction of bypass (100 mL x kg(-1) x min(-1)), cooling to 18 degrees C, then DHCA for 60 minutes. Animals were rewarmed to normothermia, weaned from bypass, and harvested after 30 minutes off bypass. Sham animals underwent sternotomy without further instrumentation. Plasma samples were taken before bypass and before harvest. Proteins differentially expressed in the cerebral neocortex between the 2 groups were determined by 2-dimensional differential gel electrophoresis using fluorescent cyanine dyes and mass spectrometry. A second group of 4 piglets were similarly randomized and, after the experiment, tissues underwent perfusion-fixation for histologic examination. RESULTS: Cardiopulmonary bypass with DHCA caused extensive histologic and ultrastructural cerebral injury. Proteomic analysis of cerebral cortex found 10 protein spots to be differentially expressed; 9 were identified by mass spectrometry to represent 6 proteins, including apolipoprotein A-1, neurofilament-M protein, and enolase. Decreased expression of plasma apolipoprotein A-1 was found in DHCA. CONCLUSIONS: The acute protein changes associated with cerebral injury in a neonatal model of cardiopulmonary bypass with DHCA have been characterized. These may direct further research aimed at attenuating injury seen from cardiopulmonary bypass with DHCA.