The Use of Lidocaine Containing Cardioplegia in Surgery for Adult Acquired Heart Disease

Myocardial protection using single dose del Nido Cardioplegia with and without topical cooling

INTRODUCTION

Del Nido cardioplegia (DN) is gaining acceptance in adult cardiac surgery but there is paucity of experimental data regarding its efficacy. We set out to assess the safety and efficacy of single-dose DN with and without topical cooling (TC) versus multi-dose blood cardioplegia (BC).

METHODS

Thirty-two healthy adult sheep had pressure-volume (PV) catheters placed in the left (LV) and right (RV) ventricle. Animals were assigned to receive cold (4°C) antegrade solution for a 60-min arrest using: (1) multi-dose (every 20 min) BC with TC (n = 11), (2) single-dose DN with TC (DN-C, n = 10), or (3) single-dose DN without TC (DN-H, n = 11). LV and RV PV-derived indexes, epicardial echocardiographic strains, and blood samples were acquired before CPB and at 1, 2, and 3 h of reperfusion. Dobutamine bolus (2.5 μg) was given after 3 h to test for myocardial reserve.

RESULTS

Time to rhythm restoration was shortest (54 ± 29 s, 118 ± 167 s, and 172 ± 170 s for DN-H, DN-C, and BC, respectively; p = 0.024) and number of shocks lowest (1.7 ± 1.8, 3.6 ± 2.8, and 5.6 ± 4.6 for DN-H, DN-C, and BC, respectively; p = 0.020) in DN-H group. Hemodynamic, load-independent myocardial function, echocardiographic, and metabolic data revealed only slight differences between groups. Troponin I levels did not differ between groups. With dobutamine, preload-recruitable stroke work of both LV (136 ± 50%, 131 ± 31%, 142 ± 58% for BC, DN-C and DN-H, respectively; p = 0.993) and RV (161 ± 67%, 185 ± 45%, 166 ± 75% for BC, DN-C and DN-H respectively; p = 0.580) increased similarly.

CONCLUSIONS

Single-dose DN cardioplegia with or without topical cooling offered comparable biventricular myocardial protection to multi-dose BC for a 60-min arrest in sheep.

Del Nido cardioplegia versus blood cardioplegia in coronary artery bypass grafting

Purpose

The del Nido cardioplegia (DC) has been extensively used in congenital heart surgery for over two decades and is becoming popular in adult cardiac surgery. We evaluated the efficacy and safety of DC, compared to conventional blood cardioplegia (BC), in adult patients undergoing isolated coronary artery bypass grafting (CABG).

Methods

This metachronous study included a total of 2330 consecutive patients who underwent isolated CABG. The study population was divided into two groups: BC group, consisting of 1165 patients (May 2012 through December 2015); and DC (del Nido) cardioplegia group consisting of 1165 patients (January 2016 through June 2018). Propensity matching yielded 735 well-matched pairs. The propensity-matched cohorts of BC and DC were compared in terms of myocardial function outcomes and other clinical outcomes to determine the efficacy and safety of both the cardioplegic solutions.

Results

There was no difference in 30-day mortality [odds ratio (OR), 0.74; 95% confidence interval (CI), 0.16-3.35, p = 0.70]. There was a significant decrease in the DC group in the postoperative events, including re-exploration rates [OR, 0.25; 95% CI, 0.118-0.568, p < 0.001], myocardial infarction [OR, 0.282; 95% CI, 0.133-0.596, p < 0.001], left ventricular dysfunction [OR, 0.60; 95% CI, 0.396-0.916, p = 0.018], and acute kidney injury (AKI) [OR, 0.255; 95% CI, 0.156-0.418, p < 0.001]. The rate of spontaneous return to sinus rhythm was significantly higher in the DC group [OR, 5.162; 95% CI, 3.701-7.198, p < 0.001]. Cardiopulmonary bypass time (95.2 ± 29.1 min vs. 82.1 ± 28.8 min, p < 0.001) and aortic cross-clamp (ACC) time (57.3 ± 19 min vs. 48.7 ± 19.0 min, p < 0.001) were higher in the DC group, but the absolute difference in ACC time was only 8 min. There was no difference in AKI requiring renal replacement therapy [OR, 0.62; 95% CI, 0.203-1.912, p = 0.40], postoperative cerebrovascular accidents [OR, 0.398; 95% CI, 0.077-2.059, p = 0.073], and postoperative ventricular arrhythmias [OR, 0.80; 95% CI, 0.456-1.916, p = 0.47].

Conclusion

This study revealed comparable clinical outcomes and effective myocardial protection with DC, compared to BC in patients undergoing isolated CABG. In addition, DC demonstrated the ease of administration with the feasibility of single-dose administration.

Outcomes of del Nido cardioplegia after surgical aortic valve replacement and coronary artery bypass grafting

OBJECTIVE

The use of del Nido cardioplegia (DNC) was initially adopted in the field of pediatric cardiac surgery. Several studies in adult patients suggested there were no differences in early postoperative outcomes as compared to blood-based cardioplegia. We sought to evaluate the impact of DNC as compared to modified Buckberg cardioplegia (BC) on early postoperative outcomes in patients undergoing surgical aortic valve replacement with and without coronary artery bypass grafting (SAVR ± CABG).

METHODS

All SAVR ± CABG procedures were switched from BC to DNC at our institute in 2012. We compared outcomes of BC (November 2007-October 2012; n = 1037) with DNC (November 2012-December 2017; n = 1067). Significant baseline differences were observed between the two groups and such differences were adjusted via inverse propensity treatment weighting.

RESULTS

After adjustment, SAVR ± CABG patients who received DNC required longer aortic cross-clamp times, while postoperative peak troponin I and creatinine kinase-MB isotype were significantly lower in the BC group. Length of hospital and intensive care unit stay were significantly shorter in the DNC group. The incidence of postoperative complications was lower in the DNC cohort. Thirty-day mortality rate was significantly lower in the DNC group (3.0% vs 4.9%, p = 0.002).

CONCLUSIONS

The use of DNC cardioplegia in our cohort of adult patients who underwent SAVR ± CABG was safe and associated with improved postoperative outcomes. However, the use of DNC may be associated with higher degrees of myocardial injury.

Del Nido cardioplegia for myocardial protection in adult cardiac surgery: a systematic review and update meta-analysis

OBJECTIVE

Although the application of del Nido cardioplegia solution (DNC) in adult cardiac surgery is accumulating, the feasibility and safety of this myocardial protection strategy in adults remains controversial. We aimed to update our previous meta-analysis to determine the myocardial protective effect of DNC versus conventional cardioplegia (CC) in adult cardiac surgery.

METHODS

A comprehensive literature search was performed using PubMed, EMBASE, the Cochrane Library, and International Clinical Trials Registry Platform databases through November 2020.

RESULTS

Thirty-seven observational studies and four randomized controlled trials (RCTs) including 21,779 patients were identified. The DNC group was associated with decreased postoperative cardiac enzymes [troponin T (cTnT) and creatine kinase-MB (CK-MB)] [standardized mean differences (SMD): -0.59, 95% confidence interval (CI): -0.99 to -0.19, p = 0.004], cardiopulmonary bypass (CPB) time (MD: -9.31, 95% CI: -13.10 to -5.51, p < 0.00001), aortic cross-clamp (ACC) time (MD: -7.20, 95% CI: -10.31 to -4.09, p < 0.00001), and cardioplegia volume (SMD: -1.95, 95% CI: -2.46 to -1.44, p < 0.00001). Intraoperative defibrillation requirement was less in the DNC group [relative risk (RR): 0.50, 95% CI: 0.33 to 0.75, p = 0.0007]. The pooled analysis revealed no significant difference in operative mortality among the patients assigned to DNC and those undergoing CC.

CONCLUSION

In adult cardiac surgery, compared to CC, myocardial protection used with DNC yield similar or better short-term clinical outcomes. More high-quality trials and RCTs reflecting long-term follow-up morbidity and mortality are required in the future to confirm these findings.

Single-Dose Del Nido Cardioplegia vs. Blood Cardioplegia in Aortic Valve Replacement Surgery

INTRODUCTION

In this study, we aimed to compare Del Nido cardioplegia (DNC) with blood cardioplegia (BC) in aortic valve replacement.

METHODS

A two-year single-institute retrospective cohort study was accomplished. Subjects who underwent aortic valve replacement surgery were divided into two groups (DNC and BC) and outcomes were compared.

RESULTS

Preoperative demographics and clinical data of the patients in both groups were similar. The time until cardiac arrest following administration of the first dose of cardioplegia was statistically significantly shorter in the BC group (47.0 sec. 25-103) than in the DNC group (63.0 sec. 48-140) (P=0.012). Cross-clamping time was longer in the BC group (48.7±12.3 min. vs. 41.5±11.8 min.) (P=0.041). Cardiopulmonary bypass time was statistically significantly shorter in the DNC group (BC 60.8±18.5 min., DNC 53.7±15.2 min.) (P=0.046). The rate of postoperative use of intravenous positive inotropic support drugs (dopamine, dobutamine, norepinephrine, etc.) for more than two hours was significantly higher in the BC group (20 [23.5%] in the BC group and nine [17.3%] in the DNC group) (P=0.035). Creatine kinase myocardial band and troponin I levels were slightly lower in patients receiving DNC, but no statistically significant difference was detected.

CONCLUSION

Del Nido cardioplegia is safe and can be used efficiently as an alternative to blood cardioplegia in isolated aortic valve replacement surgery.

Myocardial Protection in Adult Cardiac Surgery With del Nido Versus Blood Cardioplegia: A Systematic Review and Meta-Analysis

BACKGROUND

Myocardial protection in adult cardiac surgery is commonly achieved with either multidose blood cardioplegia or single-dose del Nido crystalloid cardioplegia.

AIM

The aim of this systematic review and meta-analysis was to compare the outcomes of del Nido cardioplegia versus blood cardioplegia in adult cardiac surgery.

METHOD

All English-language articles were searched in MEDLINE (PubMed), the Cochrane Central Register of Controlled Trials (CENTRAL), and Google Scholar up to March 2020, to identify randomised control trials, prospective observational studies, and retrospective analyses (with or without propensity matching) reporting any or all of the primary and secondary endpoints. The primary endpoint was all-cause mortality. Secondary endpoints included cardiopulmonary bypass (CPB) and aortic cross-clamp (AoX) time; cardioplegia volume; need for defibrillation after AoX release; intraoperative glucose; postoperative myocardial enzyme release; postoperative left ventricular ejection fraction (LVEF); incidence of postoperative acute kidney injury (AKI), atrial fibrillation (AF), stroke, and low cardiac output syndrome (LCOS); postoperative blood transfusion; duration of mechanical ventilation; and length of intensive care unit (ICU) and hospital stay.

RESULTS

Twenty-nine (29) studies were included. There was no difference in the primary outcome of mortality between the two groups (odds ratio [OR], 1.18; 95% confidence interval [CI], 0.82-1.72 [p=0.37]). del Nido cardioplegia was associated with significantly shorter CPB (mean difference [MD], -7.42 minutes; 95% CI, -12.53 to -2.31 [p=0.004]) and AoX times (MD, -6.39 minutes; 95% CI, -10.30 to -2.48 [p=0.001]), and lower cardioplegia volumes. Significantly fewer patients required defibrillation after AoX release in the del Nido group. Intraoperative glucose homeostasis was better preserved in the del Nido group. Postoperative cardiac troponin T release and the number of patients needing transfusions were less in the del Nido group. No differences were seen in postoperative LVEF, or in the incidence of AKI, stroke, AF, and LCOS. Duration of mechanical ventilation, and length of ICU and hospital stay were similar.

CONCLUSIONS

Although this meta-analysis failed to find any mortality benefits with del Nido cardioplegia, significant benefits were seen in a number of intraoperative and postoperative variables. del Nido cardioplegia is a safe and favourable alternative to blood cardioplegia in adult cardiac surgery.

Del Nido cardioplegia in coronary surgery: a propensity-matched analysis

OBJECTIVES

Del Nido cardioplegia (DNC) has been shown to be safe in adults with normal coronary arteries who are undergoing valve surgery. This study compared the effects of DNC versus traditional blood-based cardioplegia on postoperative complications in patients who underwent coronary artery bypass grafting (CABG).

METHODS

A retrospective analysis was performed on 863 patients who underwent CABG with DNC (n = 420) or control cardioplegia (CC) (n = 443) between 2014 and 2017. The full cohort of DNC and CC recipients, as well as propensity score-matched pairs, was compared regarding preoperative risk variables and outcomes.

RESULTS

The DNC and CC groups showed no significant differences in mean cardiopulmonary bypass time (53.09 vs 52.10 min, P = 0.206) or aortic cross-clamp time (32.82 vs 33.28 min, P = 0.967). The groups also showed no difference in operative mortality (2.1% vs 2.5%, P = 0.734); however, DNC use resulted in lower rates of overall infections (1.7% vs 4.3%, P = 0.024), total sternal infections (0.9% vs 3.2%, P = 0.023), postoperative atrial fibrillation (23.8% vs 30.7%, P = 0.023) and postoperative ventricular tachycardia (0.5% vs 3.4%, P = 0.002). A propensity-matching analysis (n = 335 pairs) showed similar statistically significant decreases with DNC.

CONCLUSIONS

In this large cohort of CABG patients, DNC was shown as a safe alternative to CC and was associated with lower postoperative dysrhythmia and infection rates. These findings show that DNC is safe and effective in patients whose operative interventions may require only single-dosing cardioplegia; its use in longer cases should be further explored given its low complication rate.

Long-Term Outcomes of Right Minithoracotomy Versus Hemisternotomy for Mitral Valve Repair

OBJECTIVE

Minimally invasive mitral valve repair has been increasingly adopted. Right minithoracotomy (RT) and lower hemisternotomy (HS) have each been associated with improved short-term outcomes; however, these approaches have not been directly compared to each other. The aim of this study was to compare long-term survival and durability of 2 minimally invasive approaches to mitral repair.

METHODS

We retrospectively identified all isolated mitral repairs performed via RT or HS between October 1997 and June 2018; 100 RT cases and 719 HS cases were included. Outcomes of interest were postoperative complications, long-term survival, and freedom from mitral reoperation. A Cox proportional hazard model was used to compare RT and HS to a reference cohort of full-sternotomy cases. Total observation time was 9,901 patient-years and mean follow-up time was 12.2 years.

RESULTS

Mean age was 58±12 years in the RT group and 56±13 years in the HS group (P = 0.2). The RT group had longer bypass (143 minutes vs. 112 minutes; P < 0.001) and cross-clamp times (99 minutes vs. 78 minutes; P < 0.001) compared with the HS group. There were no differences in operative mortality or 30-day outcomes. Survival at 5, 10, and 15 years was 99% (96-100), 92% (85-100), and 69% (30-100) in the RT group and 98% (97-99), 92% (90-94), and 89% (86-92) for HS (P < 0.9). There were no differences in risk-adjusted survival between RT, HS and full sternotomy. No long-term mitral reoperations occurred in the RT group and 8 (1%) occurred in the HS group (P < 0.50).

CONCLUSIONS

Minimally invasive mitral valve repair can be performed safely through RT or HS with excellent survival and durability at 15 years.

Single- versus multidose cardioplegia in adult cardiac surgery patients: A meta-analysis

OBJECTIVE

To compare outcomes of single (intervention group: del Nido [DN], and histamine-tryptophan-ketoglutarate) versus multidose (control group) cardioplegia in the adult cardiac surgery patients.

METHODS

Medical search engines were interrogated to identify relevant randomized controlled trials and propensity-score matched cohorts. Meta-analysis was conducted for primary (in-hospital/30-day mortality) and secondary (ischemic and cardiopulmonary bypass [CPB] times, reperfusion fibrillation, peak of cardiac enzymes, myocardial infarction) endpoints. Subgroup analyses were conducted for study design and type of intervention, and meta-regression for primary outcome included type of surgery and left ventricular ejection fraction as moderators.

RESULTS

Ten randomized controlled trials and 13 propensity-score matched cohorts were included, reporting on 5516 patients. Estimates are expressed as (parameter value [OR, odds ratio; MD, mean difference; SMD, standardized mean difference]/unit of measure [95% confidence interval], P value). DN reduced ischemic time (MD, -7.18 minutes [-12.52 to -1.84], P < .01), CPB time (MD, -10.44 minutes [-18.99 to -1.88], P .01), reperfusion fibrillation (OR, 0.16 [0.05-0.54], P < .01), and cardiac enzymes (SMD -0.17 [-0.29, 0.05], P < .01) compared with multidose cardioplegia. None of these beneficial effects were reproduced by histamine-tryptophan-ketoglutarate, which instead increased CPB time (MD, 2.04 minutes [0.73-3.37], P < .01) and reperfusion fibrillation (OR, 1.80 [1.20-2.70], P < .01). There was no difference in mortality and myocardial infarction between single and multidose, independently of type of surgery or left ventricular ejection fraction.

CONCLUSIONS

DN decreases operative times, reperfusion fibrillation, and surge of cardiac enzymes compared with multidose cardioplegia.

Excellent Restoration of Left Ventricular Compliance After Prolonged Del Nido Single-Dose Cardioplegia in an In Vivo Piglet Model

Del Nido cardioplegia (DN) is used in congenital heart surgery and recently in adults, a single dose has been administered. However, the tolerable ischemic time has not been established. The objective is to evaluate the left ventricular (LV) function recovery and accompanying biochemical and histologic markers to clarify the tolerable ischemic time in an in vivo cardiopulmonary bypass (CPB) piglet model. Twenty-one piglets were subjected to either 90 minutes (with or without topical cooling; TC) or 120 minutes (with TC) of global ischemia induced by single-dose DN, while the other 7 served as the control group (CPB only). The CPB temperature was established with a perfusion temperature of 30°C. The LV function recovery was assessed by the percent change in end-systolic elastance (Ees) and the end-diastolic pressure-volume relationship (EDPVR). Creatine kinase-MB (CK-MB) levels and the mitochondrial score were also assessed. LV contractility assessed by %Ees after 90 and 120 minutes of ischemia (89.3 ± 20.6% and 57.9 ± 17.8%) was lower compared with the control group (122.6 ± 35.8%, P = 0.001). Conversely, LV compliance assessed by %EDPVR was preserved in both groups (102.7 ± 28.2% and 88.5 ± 24.0%), which was comparable to the control group (105.8 ± 36.9%, P = 0.531). There was no change in LV contractility after 90 minutes of ischemia with or without TC (89.3 ± 20.6% or 84.8 ± 16.2%, P = 0.657), whereas LV compliance was lower but not statistically different without TC (102.7 ± 28.2% vs 78.0 ± 38.9%). CK-MB and the mitochondrial score were equivalent between all groups. The proposed single-dose ischemic time for redosing is 90 minutes using TC.

A Systematic Review and Meta-Analysis of del Nido Versus Conventional Cardioplegia in Adult Cardiac Surgery

OBJECTIVE

Del Nido cardioplegia (DC) has been used extensively in pediatric cardiac surgery but the efficacy and safety in adults remains uncertain. Our objective was to perform a systematic review and meta-analysis comparing DC and blood cardioplegia (BC) in our primary endpoint of 30-day or in-hospital mortality as well as other efficacy and safety endpoints.

METHODS

Both MEDLINE and EMBASE were searched from 1996 to 2017 for studies comparing DC and BC. Data were extracted by 2 independent investigators and aggregated in a random effects model.

RESULTS

One randomized controlled trial (n = 89), 7 adjusted (n = 1,104), and 5 unadjusted observational studies (n = 717) were included. There was no difference in in-hospital mortality between DC and BC (relative risk:0.67, 95% confidence interval [CI]: 0.22, 2.07; P = 0.49). DC reduced cardioplegia volume requirements (mean difference [MD]:-1.1 L, 95% CI, -1.6, -0.6; P < 0.0001), aortic cross-clamp time (MD: -8 minutes, 95% CI, -12, -3; P = 0.0004), and cardiopulmonary bypass (CPB) times (MD: -8 minutes, 95% CI, -14, -3; P = 0.03). DC reduced troponin release (standardized MD: -0.3, 95% CI, -0.5, -0.1; P = 0.001). In-hospital outcomes of stroke, atrial fibrillation, acute kidney injury/dialysis, low cardiac output state, blood transfusion, reoperation rate, postoperative left ventricular EF, intensive care unit length of stay (LOS), and in-hospital LOS were comparable between groups.

CONCLUSIONS

DC is a safe alternative to BC in routine adult cardiac surgery. Its use is associated with reduction in CPB and aortic cross-clamp times and may potentially offer improved myocardial protection.

Comparison of del Nido Cardioplegia with Blood Cardioplegia in Coronary Artery Bypass Grafting Combined with Mitral Valve Replacement

OBJECTIVE

To compare del Nido cardioplegia (DNC) with blood cardioplegia (BC) in coronary artery bypass grafting (CABG) combined with mitral valve replacement.

METHODS

A 3-year single-center retrospective cohort study was carried out. Subjects who underwent CABG (up to triple bypass) combined with mitral valve replacement were divided into DNC and BC groups. Each group had thirty subjects.

RESULTS

Both groups demonstrated similar baseline characteristics, including age, gender, cardiac/non-cardiac comorbidity, and preoperative echocardiographic parameters. Compared with the BC group, the DNC group demonstrated significantly lower cardioplegia volume (BC = 1130.00±194.1 mL, DNC = 884.33±156.8 mL, P=0.001), cardiopulmonary bypass time (DNC = 110.90±12.52 min, BC = 121.70±13.57 min, P=0.002), aortic clamp time (DNC = 91.37±11.58 min, BC = 101.37±13.87 min, P=0.004), and need for intraoperative defibrillation (DNC = 6 events, BC = 21 events, P=0.001). Postoperative creatine kinase-MB levels and troponin levels were significantly lower in the DNC group than in the BC group. Postoperative haemoglobin and haematocrit levels were significantly higher in the DNC group than in the BC group. The intubation period (hours) in intensive care unit (ICU) was significantly small in the BC group (DNC = 8.13±12.21, BC = 6.82±1.57, P=0.037); however, ICU stay, total hospital stay, and postoperative complication rates were not significantly different between them. At pre-discharge echocardiography, the DNC group demonstrated significantly higher ejection fraction rates than the BC group (47.79±5.50 and 45.72±5.86, respectively, P=0.005).

CONCLUSION

DNC presented better intraoperative and postoperative parameters and it is an effective and safe alternative to BC for CABG combined with mitral valve replacement.

Molecular Genetics of Lidocaine-Containing Cardioplegia in the Human Heart During Cardiac Surgery

BACKGROUND

During cardiac surgery with cardiopulmonary bypass, delivery of cardioplegia solution to achieve electromechanical cardiac quiescence is obligatory. The addition of lidocaine to cardioplegia has advantages, although its consequences at a molecular level remain unclear. We performed whole-genome RNA sequencing of the human left ventricular (LV) myocardium to elucidate the differences between whole-blood (WB) cardioplegia with and without addition of lidocaine (LC) on gene expression.

METHODS

We prospectively enrolled 130 patients undergoing aortic valve replacement surgery. Patients received high-potassium blood cardioplegia either with (n = 37) or without (n = 93) lidocaine. The LV apex was biopsied at baseline, and after an average of 74 minutes of cold cardioplegic arrest. We performed differential gene expression analysis for 18,258 genes between these 2 groups. Clinical and demographic variables were adjusted in the model. Gene ontology (GO) and network enrichment analysis of the retained genes were performed using g:Profiler and Cytoscape.

RESULTS

A total of 1,298 genes were differentially expressed between cardioplegic treatments. Compared with the WB group, genes upregulated in the LC group were identified by network enrichment to play a protective role in ischemic injury by inhibiting apoptosis, increasing transferrin endocytosis, and increasing cell viability. Downregulated genes in the LC group were identified to play a role in inflammatory diseases, oxygen transport, and neutrophil aggregation.

CONCLUSIONS

The addition of lidocaine to cardioplegia had pronounced effects on a molecular level with genes responsible for decreased inflammation, reduced intracellular calcium binding, enhanced antiapoptotic protection, augmented oxygen accessibility through transferrins, and increased cell viability showing measurable differences.

The use of del Nido cardioplegia in adult cardiac surgery: A prospective randomized trial

OBJECTIVES

The del Nido cardioplegia solution has been used extensively in congenital heart surgery for more than 20 years and more recently for adults. This randomized controlled trial examined whether expanding this technique to adult cardiac surgery confers benefits in surgical workflow and clinical outcome compared with blood-based cardioplegia.

METHODS

Adult first-time coronary artery bypass grafting (CABG), valve, or CABG/valve surgery patients requiring cardiopulmonary bypass (CPB) were randomized to del Nido cardioplegia (n = 48) or whole blood cardioplegia (n = 41). Primary outcomes assessed myocardial preservation. Troponin I was measured at baseline, 2 hours after CPB termination, 12 and 24 hours after cardiovascular intensive care unit admission. Alpha was set at P < .001.

RESULTS

Preoperative characteristics were similar between groups, including age, Society of Thoracic Surgeons risk score, CABG, and valve procedures. There was no significant difference on CPB time (97 vs 103 minutes; P = .288) or crossclamp time (70 vs 83 minutes; P = .018). The del Nido group showed higher return to spontaneous rhythm (97.7% vs 81.6%; P = .023) and fewer patients required inotropic support (65.1% vs 84.2%; P = .050), but did not reach statistical significance. Incidence of Society of Thoracic Surgeons-defined morbidity was low, with no strokes, myocardial infarctions, renal failure, or operative deaths. For del Nido group patients, troponin levels did not increase as much as for control patients (P = .040), but statistical significance was not reached.

CONCLUSIONS

Evidence from this study suggests del Nido cardioplegia use in routine adult cases may be safe, result in comparable clinical outcomes, and streamline surgical workflow. The trend for troponin should be investigated further because it may suggest superior myocardial protection with the del Nido solution.

A protocol to study ex vivo mouse working heart at human-like heart rate

Genetically modified mice are widely used as experimental models to study human heart function and diseases. However, the fast rate of normal mouse heart at 400-600bpm limits its capacity of assessing kinetic parameters that are important for the physiology and pathophysiology of human heart that beats at a much slower rate (75-180bpm). To extend the value of mouse models, we established a protocol to study ex vivo mouse working hearts at a human-like heart rate. In the presence of 300μM lidocaine to lower pacemaker and conductive activities and prevent arrhythmia, a stable rate of 120-130bpm at 37°C is achieved for ex vivo mouse working hearts. The negative effects of decreased heart rate on force-frequency dependence and lidocaine as a myocardial depressant on intracellular calcium can be compensated by using a higher but still physiological level of calcium (2.75mM) in the perfusion media. Multiple parameters were studied to compare the function at the human-like heart rate with that of ex vivo mouse working hearts at the standard rate of 480bpm. The results showed that the conditions for slower heart rate in the presence of 300μM lidocaine did not have depressing effect on left ventricular pressure development, systolic and diastolic velocities and stroke volume with maintained positive inotropic and lusitropic responses to β-adrenergic stimulation. Compared with that at 480bpm, the human-like heart rate increased ventricular filling and end diastolic volume with enhanced Frank-Starling responses. Coronary perfusion was increased from longer relaxation time and interval between beats whereas cardiac efficiency was significantly improved. Although the intrinsic differences between mouse and human heart remain, this methodology for ex vivo mouse hearts to work at human-like heart rate extends the value of using genetically modified mouse models to study cardiac function and human heart diseases.