Long Term Survival Benefits of Different Conduits Used in Coronary Artery Bypass Graft Surgery- A Single Institutional Practice Over 20 Years.

Objective: This study determined hazard factors and long-term survival rate of total arterial coronary artery bypass graft surgery over 20 years in an extensively large, population-based cohort. Methods: A total of 2979 patients who underwent isolated CABG from April 1999 to March 2020 were studied in 4 groups- Group-A (bilateral internal mammary artery ± radial artery), Group-B (single internal mammary artery + radial artery ± saphenous vein), Group-C (single internal mammary artery ± saphenous vein; no radial artery), and Group-D (radial artery ± saphenous vein; no internal mammary artery). The study endpoints analysed the correlation between the number and types of grafts with the survival time following isolated CABG surgery. Results: The total arterial revascularization (Group A) group had an admirable mean long-term survival of ~19 years, compared to 18.6 years (Group B), 15.86 years (Group C), and 10.99 years (Group D). A Kaplan-Meier curve demonstrated confidence interval (CI) for study groups- (95% CI 18.33-19.94), (95% CI 18.14-19.06), (95% CI 15.40-16.32), and (95% CI 9.61-12.38) in Group A, B, C, D respectively. In the Holm-Sidak method analysis, significant associations existed between the number of arterial grafts and the long-term outcome. A statistically significant (P≤0.05) long-term survival advantage for arterial grafting was demonstrated, especially total arterial revascularisation over all other combinations except single internal mammary artery + radial artery grafting. Conclusion: In this series, over 20 years, total arterial CABG use has excellent long-term survival, achieving complete myocardial revascularisation. There is no significant difference between the BIMA group and SIMA with radial artery. However, there is a reduced survival with decreased use of arterial conduits.

Survival and Independent Predictors of Mortality Following Coronary Artery Bypass Graft Surgery in a Single-Unit Practice in the United Kingdom Over 20 Years.

BACKGROUND:  The types of graft conduits and surgical techniques may impact the long-term outcomes of patients after coronary artery bypass graft (CABG) revascularization. This study observed a long-term survival rate following CABG surgery over 20 years in the United Kingdom. METHODS:  A total of 2979 isolated CABG patients were studied from 1999 to 2020, and postoperative data were obtained from the hospital-recorded mortality by the data quality team of the information department. Postdischarge survival was estimated using the Kaplan-Meier method, and statistical significance was obtained with log-rank tests and the Gehan-Breslow test, and the Holm-Sidak method was used for multiple pairwise comparisons. RESULTS:  The study observed male predominance (80%), and the median age was statistically significant (P <0.001) among the groups, 66 years (interquartile range 58-73) and 72 years (interquartile range 66-78) in survivor and non-survivor groups, respectively. In the Holm-Sidak method analysis, the best survival rate (mean 18.7 years) was observed in the total arterial group with significantly decreased survival for the mixed arterial and venous group (mean 16.12 years) and only the vein group (10.44 years). The Cox regression model observed that the New York Heart Association (NYHA) class III-IV (HR 1.57), chest re-exploration (HR 2.14), preoperative dialysis (HR 3.13), and redo surgery (HR 3.04) were potential predictors of the postoperative mortality (P ≤0.05). CONCLUSION:  In our series over 20 years, albeit off-pump and on-pump CABG observed similar survival rates, the total arterial myocardial revascularization population has significantly better long-term survival benefits.

The smoking-dyslipidaemia dyad: A potent synergistic risk for atherosclerotic coronary artery disease.

BACKGROUND: Smoking and dyslipidaemia are known individual risk factors of coronary artery disease (CAD). The present study examined the combined risk of smoking and dyslipidaemia on coronary atherosclerosis. METHODS: Coronary artery calcium (CAC), measured by cardiac CT, was used to assess the extent of CAD, which was related to smoking and dyslipidaemia using logistic regression, adjusted for age, sex, hypertension, BMI and family history of ischaemic heart disease. RESULTS: Seventy-one patients (46 men, 25 women: median age of 53.7yrs; IQR = 47.0-59.5) were recruited. The mean log10 CAC score in never-smokers without dyslipidaemia (reference group) was 0.37 (SD = 0.73), while the value in those with a history of smoking was 0.44 ± 0.48 (mean difference: 0.07, 95%CI:-0.67 to 0.81, p = 0.844), dyslipidaemia was 1.07 ± 1.08 (mean difference: 0.71, 95%CI: 0.24 to 1.17, p = 0.003), and both risk factors was 1.82 ± 0.64 (mean difference: 1.45, 95%CI:0.88 to 2.02, p < 0.001). For individuals in the reference group, the proportions with none, one and multiple vessel disease were 80.6%, 16.1% and 3.2%; for those with a history of smoking or with dyslipidaemia were 50.0%, 25.0% and 25.0%; and for those with both risk factors were 8.3%, 25.0% and 66.7%. Patients with a history of both risk factors had greater adjusted risks of having one- vessel disease - OR = 14.3 (95%CI = 2.1-98.2) or multiple vessel disease: OR = 51.8 (95%CI = 4.2-609.6). CONCLUSIONS: Smoking and dyslipidaemia together are associated with high coronary artery calcification and CAD, independent of other major risk factors.

Donor hearts in the Sydney Heart Bank: reliable control but is it 'normal' heart?

Human heart samples from the Sydney Heart Bank have become a de facto standard against which others can be measured. Crucially, the heart bank contains a lot of donor heart material: for most researchers this is the hardest to obtain and yet is necessary since we can only study the pathological human heart in comparison with a control, preferably a normal heart sample. It is not generally realised how important the control is for human heart studies. We review our studies on donor heart samples. We report the results obtained with 17 different donor samples collected from 1994 to 2011 and measured from 2005 to 2015 by our standard methodology for in vitro motility and troponin I phosphorylation measurements. The donor heart sample parameters are consistent between the hearts, over time and with different operators indicating that Sydney Heart Bank donor hearts are a valid baseline control for comparison with pathological heart samples. We also discuss to what extent donor heart samples are representative of the normal heart.

Sex differences in the agreement between left ventricular ejection fraction measured by myocardial perfusion scintigraphy and by echocardiography.

BACKGROUND: Left ventricular ejection fraction (LVEF) is generally measured by echocardiography but is increasingly available with myocardial perfusion scintigraphy. With myocardial perfusion scintigraphy, the threshold of LVEF below which there is a risk for myocardial infarct or sudden cardiac death is higher for women (51%) than for men (43%). We tested the hypothesis that such a sex difference may also occur with echocardiography and myocardial perfusion scintigraphy. METHODS: Four hundred and four men, mean age = 67.7 ± SD = 12.3 yr; 339 women, 67.7 ± 11.7 yr had separate myocardial perfusion scintigraphy and echocardiography examinations within six months. A subset of 327 of these patients (181 men, 68.8 ± 12.1 yr; 146 women, 66.4 ± 12.1 yr) had examinations within one month and were additionally analysed as this sub-group. Myocardial perfusion scintigraphy and echocardiography were used to measure LVEF at rest and their agreement (neither considered as a reference method) was assessed by Bland-Altman plots: LVEF difference (myocardial perfusion scintigraphy minus echocardiography ) against average LVEF ( MPS + Echo 2 ). RESULTS: Of patients who had myocardial perfusion scintigraphy and echocardiography performed within six months, mean LVEF difference = +1.1% (95% limits of agreement: -19.3 to +21.6) in men but +10.9% (-10.7 to +32.5) in women. LVEF difference diverged from zero marginally in men (mean difference = +1.1, 95%CI = +0.1 to +2.1, p = 0.028) but more in women (+10.9, +9.8 to +12.1, p < 0.001). The LVEF difference correlated with average LVEF itself in both men (r = 0.305, p < 0.001) and women (r = 0.361, p < 0.001), and with age in women (r = 0.117, p = 0.031). Similar results were observed for the subset. CONCLUSIONS: Caution should be taken when interpreting LVEF measured by different techniques due to their wide limits of agreement and systematic bias, more markedly in women.

Ischemic preconditioning-an unfulfilled promise.

Myocardial reperfusion injury has been identified as a key determinant of myocardial infarct size in patients undergoing percutaneous or surgical interventions. Although the molecular mechanisms underpinning reperfusion injury have been elucidated, attempts at translating this understanding into clinical benefit for patients undergoing cardiac interventions have produced mixed results. Ischemic conditioning has been applied before, during, or after an ischemic insult to the myocardium and has taken the form of local induction of ischemia or ischemia of distant tissues. Clinical studies have confirmed the safety of differing conditioning techniques, but the benefit of such techniques in reducing hard clinical event rates has produced mixed results. The aim of this article is to review the role of ischemic conditioning in patients undergoing percutaneous and surgical coronary revascularization.

Benefits of a quadripolar left ventricular lead in patients undergoing cardiac resynchronization therapy with underlying myocardial scar.

We present a case of a 76-year-old man with ischemic cardiomyopathy. Cardiac magnetic resonance imaging demonstrated severe left ventricular (LV) impairment with possibility of scar formation. Cardiac resynchronization therapy was employed with the aid of a novel quadripolar LV lead. The quadripolar LV lead can be programmed for 10 different pacing configurations, allowing the electrophysiologist freedom to optimize the vector around scar and also avoid phrenic nerve stimulation without the requirement of LV lead repositioning.

Myofibrillar Ca(2+) sensitivity is uncoupled from troponin I phosphorylation in hypertrophic obstructive cardiomyopathy due to abnormal troponin T.

AIMS: We studied the relationship between myofilament Ca(2+) sensitivity and troponin I (TnI) phosphorylation by protein kinase A at serines 22/23 in human heart troponin isolated from donor hearts and from myectomy samples from patients with hypertrophic obstructive cardiomyopathy (HOCM). METHODS AND RESULTS: We used a quantitative in vitro motility assay. With donor heart troponin, Ca(2+) sensitivity is two- to three-fold higher when TnI is unphosphorylated. In the myectomy samples from patients with HOCM, the mean level of TnI phosphorylation was low: 0.38 ± 0.19 mol Pi/mol TnI compared with 1.60 ± 0.19 mol Pi/mol TnI in donor hearts, but no difference in myofilament Ca(2+) sensitivity was observed. Thus, troponin regulation of thin filament Ca(2+) sensitivity is abnormal in HOCM hearts. HOCM troponin (0.29 mol Pi/mol TnI) was treated with protein kinase A to increase the level of phosphorylation to 1.56 mol Pi/mol TnI. No difference in EC(50) was found in thin filaments containing high and low TnI phosphorylation levels. This indicates that Ca(2+) sensitivity is uncoupled from TnI phosphorylation in HOCM heart troponin. Coupling could be restored by replacing endogenous troponin T (TnT) with the recombinant TnT T3 isoform. No difference in Ca(2+) sensitivity was observed if TnI was exchanged into HOCM heart troponin or if TnT was exchanged into the highly phosphorylated donor heart troponin. Comparison of donor and HOCM heart troponin by mass spectrometry and with adduct-specific antibodies did not show any differences in TnT isoform expression, phosphorylation or any post-translational modifications. CONCLUSION: An abnormality in TnT is responsible for uncoupling myofibrillar Ca(2+) sensitivity from TnI phosphorylation in the septum of HOCM patients.

Normal passive viscoelasticity but abnormal myofibrillar force generation in human hypertrophic cardiomyopathy.

Hypertrophic cardiomyopathy (HCM) is characterized by left ventricular hypertrophy, increased ventricular stiffness and impaired diastolic filling. We investigated to what extent myocardial functional defects can be explained by alterations in the passive and active properties of human cardiac myofibrils. Skinned ventricular myocytes were prepared from patients with obstructive HCM (two patients with MYBPC3 mutations, one with a MYH7 mutation, and three with no mutation in either gene) and from four donors. Passive stiffness, viscous properties, and titin isoform expression were similar in HCM myocytes and donor myocytes. Maximal Ca(2+)-activated force was much lower in HCM myocytes (14 ± 1 kN/m(2)) than in donor myocytes (23 ± 3 kN/m(2); P<0.01), though cross-bridge kinetics (k(tr)) during maximal Ca(2)(+) activation were 10% faster in HCM myocytes. Myofibrillar Ca(2)(+) sensitivity in HCM myocytes (pCa(50)=6.40 ± 0.05) was higher than for donor myocytes (pCa(50)=6.09 ± 0.02; P<0.001) and was associated with reduced phosphorylation of troponin-I (ser-23/24) and MyBP-C (ser-282) in HCM myocytes. These characteristics were common to all six HCM patients and may therefore represent a secondary consequence of the known and unknown underlying genetic variants. Some HCM patients did however exhibit an altered relationship between force and cross-bridge kinetics at submaximal Ca(2+) concentrations, which may reflect the primary mutation. We conclude that the passive viscoelastic properties of the myocytes are unlikely to account for the increased stiffness of the HCM ventricle. However, the low maximum Ca(2+)-activated force and high Ca(2+) sensitivity of the myofilaments are likely to contribute substantially to any systolic and diastolic dysfunction, respectively, in hearts of HCM patients.

Functional analysis of a unique troponin c mutation, GLY159ASP, that causes familial dilated cardiomyopathy, studied in explanted heart muscle.

BACKGROUND: Familial dilated cardiomyopathy can be caused by mutations in the proteins of the muscle thin filament. In vitro, these mutations decrease Ca(2+) sensitivity and cross-bridge turnover rate, but the mutations have not been investigated in human tissue. We studied the Ca(2+)-regulatory properties of myocytes and troponin extracted from the explanted heart of a patient with inherited dilated cardiomyopathy due to the cTnC G159D mutation. METHODS AND RESULTS: Mass spectroscopy showed that the mutant cTnC was expressed approximately equimolar with wild-type cTnC. Contraction was compared in skinned ventricular myocytes from the cTnC G159D patient and nonfailing donor heart. Maximal Ca(2+)-activated force was similar in cTnC G159D and donor myocytes, but the Ca(2+) sensitivity of cTnC G159D myocytes was higher (EC(50) G159D/donor=0.60). Thin filaments reconstituted with skeletal muscle actin and human cardiac tropomyosin and troponin were studied by in vitro motility assay. Thin filaments containing the mutation had a higher Ca(2+) sensitivity (EC(50) G159D/donor=0.55 + or - 0.13), whereas the maximally activated sliding speed was unaltered. In addition, the cTnC G159D mutation blunted the change in Ca(2+) sensitivity when TnI was dephosphorylated. With wild-type troponin, Ca(2+) sensitivity was increased (EC(50) P/unP=4.7 + or - 1.9) but not with cTnC G159D troponin (EC(50) P/unP=1.2 + or - 0.1). CONCLUSIONS: We propose that uncoupling of the relationship between phosphorylation and Ca(2+) sensitivity could be the cause of the dilated cardiomyopathy phenotype. The differences between these data and previous in vitro results show that native phosphorylation of troponin I and troponin T and other posttranslational modifications of sarcomeric proteins strongly influence the functional effects of a mutation.

Evidence from human myectomy samples that MYBPC3 mutations cause hypertrophic cardiomyopathy through haploinsufficiency.

RATIONALE: Most sarcomere gene mutations that cause hypertrophic cardiomyopathy are missense alleles that encode dominant negative proteins. The potential exceptions are mutations in the MYBPC3 gene (encoding cardiac myosin-binding protein-C [MyBP-C]), which frequently encode truncated proteins. OBJECTIVE: We sought to determine whether there was evidence of haploinsufficiency in hypertrophic cardiomyopathy caused by MYBPC3 mutations by comparing left ventricular muscle from patients undergoing surgical myectomy with samples from donor hearts. METHODS AND RESULTS: MyBP-C protein and mRNA levels were quantitated using immunoblotting and RT-PCR. Nine of 37 myectomy samples had mutations in MYBPC3: 2 missense alleles (Glu258Lys, Arg502Trp) and 7 premature terminations. No specific truncated MyBP-C peptides were detected in whole muscle homogenates of hypertrophic cardiomyopathy tissue. However, the overall level of MyBP-C in myofibrils was significantly reduced (P<0.0005) in tissue containing either a truncation or missense MYBPC3 mutation: 0.76+/-0.03 compared with 1.00+/-0.05 in donor and 1.01+/-0.06 in non-MYBPC3 mutant myectomies. CONCLUSIONS: The absence of any detectable truncated MyBP-C argues against its incorporation in the myofiber and any dominant negative effect. In contrast, the lowered relative level of full length protein in both truncation and missense MYBPC3 mutations argues strongly that haploinsufficiency is sufficient to cause the disease.

Myosin binding protein C phosphorylation in normal, hypertrophic and failing human heart muscle.

Phosphorylation of myosin binding protein C (MyBP-C) was investigated in intraventricular septum samples taken from patients with hypertrophic cardiomyopathy undergoing surgical septal myectomy. These samples were compared with donor heart muscle, as a well-characterised control tissue, and with end-stage failing heart muscle. MyBP-C was partly purified from myofibrils using a modification of the phosphate-EDTA extraction of Hartzell and Glass. MyBP-C was separated by SDS-PAGE and stained for phosphoproteins using Pro-Q Diamond followed by total protein staining using Coomassie Blue. Relative phosphorylation level was determined from the ratio of Pro-Q Diamond to Coomassie Blue staining of MyBP-C bands as measured by densitometry. We compared 9 myectomy samples and 9 failing heart samples with 9 donor samples. MyBP-C phosphorylation in pathological muscle was lower than in donor (myectomy 40+/-2% of donor, P<0.0001; failing 45+/-3% of donor, P<0.0001). 6 myectomy samples were identified with MYBPC3 mutations, one with MYH7 mutation and two remained unknown, but there was no correlation between MYBPC3 mutation and MyBP-C phosphorylation level. In order to determine the number of phosphorylated sites in human cardiac MyBP-C samples, we phosphorylated the recombinant MyBP-C fragment, C0-C2 (1-453) with PKA using (gamma32)P-ATP up to 3.5 mol Pi/mol C0-C2. This measurement of phosphorylation was used to calibrate measurements of phosphorylation in SDS-PAGE using Pro-Q Diamond stain. The level of phosphorylation in donor heart MyBP-C was calculated to be 4.6+/-0.6 mol Pi/mol and 2.0+/-0.3 mol Pi/mol in myectomy samples. We conclude that MyBP-C is a highly phosphorylated protein in vivo and that diminished MyBP-C phosphorylation is a feature of both end-stage heart failure and hypertrophic cardiomyopathy.

The molecular phenotype of human cardiac myosin associated with hypertrophic obstructive cardiomyopathy.

AIM: The aim of the study was to compare the functional and structural properties of the motor protein, myosin, and isolated myocyte contractility in heart muscle excised from hypertrophic cardiomyopathy patients by surgical myectomy with explanted failing heart and non-failing donor heart muscle. METHODS: Myosin was isolated and studied using an in vitro motility assay. The distribution of myosin light chain-1 isoforms was measured by two-dimensional electrophoresis. Myosin light chain-2 phosphorylation was measured by sodium dodecyl sulphate-polyacrylamide gel electrophoresis using Pro-Q Diamond phosphoprotein stain. RESULTS: The fraction of actin filaments moving when powered by myectomy myosin was 21% less than with donor myosin (P = 0.006), whereas the sliding speed was not different (0.310 +/- 0.034 for myectomy myosin vs. 0.305 +/- 0.019 microm/s for donor myosin in six paired experiments). Failing heart myosin showed 18% reduced motility. One myectomy myosin sample produced a consistently higher sliding speed than donor heart myosin and was identified with a disease-causing heavy chain mutation (V606M). In myectomy myosin, the level of atrial light chain-1 relative to ventricular light chain-1 was 20 +/- 5% compared with 11 +/- 5% in donor heart myosin and the level of myosin light chain-2 phosphorylation was decreased by 30-45%. Isolated cardiomyocytes showed reduced contraction amplitude (1.61 +/- 0.25 vs. 3.58 +/- 0.40%) and reduced relaxation rates compared with donor myocytes (TT(50%) = 0.32 +/- 0.09 vs. 0.17 +/- 0.02 s). CONCLUSION: Contractility in myectomy samples resembles the hypocontractile phenotype found in end-stage failing heart muscle irrespective of the primary stimulus, and this phenotype is not a direct effect of the hypertrophy-inducing mutation. The presence of a myosin heavy chain mutation causing hypertrophic cardiomyopathy can be predicted from a simple functional assay.

From genotype to phenotype: a longitudinal study of a patient with hypertrophic cardiomyopathy due to a mutation in the MYBPC3 gene.

Many of the links between the genotype and phenotype in hypertrophic cardiomyopathy remain unexplained. In this unique longitudinal study we have investigated a patient with classical clinical phenotypic features of hypertrophic obstructive cardiomyopathy, with a known mutation in MYBPC3, the most commonly affected gene in this disease. By collecting cardiac tissue from the patient at the time of surgical myectomy for relief of left ventricular outflow tract obstruction, we have been able to examine the structure of the myocytes and the functional differences that occur in MyBP-C mutated HCM cardiac tissue from single protein level, onto single cardiomyocyte contractility, through to whole organ function as assessed clinically by echocardiography.

Troponin phosphorylation and regulatory function in human heart muscle: dephosphorylation of Ser23/24 on troponin I could account for the contractile defect in end-stage heart failure.

We made quantitative measurements of phosphorylation in troponin isolated from 6 non-failing donor hearts and 6 explanted hearts with end-stage heart failure in SDS-PAGE gels using Pro-Q Diamond phosphoprotein stain. The troponin T phosphorylation level was the same in troponin from failing and non-failing heart (3.1 mol Pi/mol). However, troponin I phosphorylation was significantly lower in failing (0.37+/-0.18 mol Pi/mol) compared with non-failing heart troponin (2.25+/-0.36 mol Pi/mol). Levels of troponin I PKA-dependent phosphorylation, measured with a phosphoserine 23/24-specific antibody, were also significantly lower in failing heart troponin (0.19+/-0.06 mol Pi/mol) compared to non-failing troponin (1.14+/-0.09 mol Pi/mol). We calculate that there is phosphorylation in addition to serine 23/24 of 1.11+/-0.34 mol Pi/mol in non-failing reduced to 0.18+/-0.17 mol Pi/mol in failing heart troponin, attributed to phosphorylation on the PKC sites. To test for the functional role of troponin I phosphorylation, the native troponin I from either non-failing or failing heart troponin was exchanged for a recombinant (unphosphorylated) human cardiac troponin I. Thin filament Ca(2+)-regulatory function was studied with the quantitative in vitro motility assay: thin filaments containing the replaced troponin I resulted in a failing phenotype of a 17-26% reduced sliding speed and an increased Ca(2+)-sensitivity relative to non-failing troponin (EC(50) TnI-exchanged/non-failing=0.57, p<0.001). When exchanged with troponin I phosphorylated with PKA motility parameters reverted to a pattern indistinguishable from non-failing troponin (p=0.35-0.75). We suggest that changes in troponin function can account for the contractile abnormality in failing heart muscle and that the functional changes in troponin are due to reduced phosphorylation of troponin I at the PKA sites.

Fatal hypertrophic cardiomyopathy and nemaline myopathy associated with ACTA1 K336E mutation.

We report on a 2-year-old male child with both nemaline myopathy and hypertrophic cardiomyopathy (HCM). Sequencing of the ACTA1 gene showed a "de novo" missense heterozygous mutation a>g in exon 7 (Lys336Glu). Two-dimensional electrophoresis showed 28% mutant actin present in his muscle biopsy. Actin was isolated from the muscle biopsy and examined by in vitro motility assay. The sliding speed was 13+/-3% less than normal and the affinity of actin for the Z-line protein alpha-actinin was reduced 10 fold. This is the first report on a hypertrophic cardiomyopathy associated with nemaline myopathy and an ACTA1 mutation.

A commentary on clinical trials in chronic heart failure.

Heart failure is a common condition and becoming more common. Many treatments have been evaluated in large clinical trials during the last few decades. These trials can be criticized but do provide an evidence base for treatment, probably greater than for most other clinical conditions. Weaknesses exist in relation to age, ejection fraction, and gender. Most trials have included patients 10 years younger than those in the general population. There is little evidence for efficacy in patients with a near normal ejection fraction. Few women have been included in trials.