Diltiazem provides higher internal mammary artery flow than nitroglycerin during coronary artery bypass grafting surgery

Role of magnesium alone or in combination with diltiazem and/or amiodarone in prevention of atrial fibrillation following off-pump coronary artery bypass grafting

Objectives

In this study the authors have tried to examine the role of magnesium alone or in combination with diltiazem and / or amiodarone in prevention of atrial fibrillation (AF) following off-pump coronary artery bypass grafting (CABG).

Background

AF after CABG is common and contributes to morbidity and mortality. Various pharmacological preventive measures including magnesium, amiodarone, diltiazem, and combination therapy among others have been tried to lower the incidence of AF. Most of the studies have been performed in patients undergoing conventional on-pump CABG. In this uncontrolled trial, efficacy of magnesium alone or in combination with amiodarone and / or diltiazem has been studied in patients undergoing off-pump CABG.

Methods

One hundred and fifty patients undergoing off-pump CABG were divided into 3 groups, Group M (n=21) received intraoperative magnesium infusion at 30mg/ kg over 1 hour after midline sternotomy; Group MD (n=78) received magnesium infusion in similar manner with diltiazem infusion at 0.05 μg/kg/hr throughout the intraoperative period; Group AMD (n=51) received preoperative oral amiodarone at a dose of 200 mg three times a day for 3 days followed by 200 mg twice daily for another 3 days followed by 200 mg once daily till the day of surgery along with magnesium and diltiazem infusion as in other groups. AF lasting more than 10 min or requiring medical intervention was considered as AF.

Results

The overall incidence of postoperative AF was 12.6% with 11.7% in group AMD, 19% in group M, and 11.5% in group MD, which was not statistically significant.

Conclusions

It is concluded that the use of amiodarone and/or diltiazem in addition to magnesium did not result in additional benefit of lowering the incidence of AF.

Perioperative diltiazem therapy was not associated with improved perioperative and long-term outcomes in patients undergoing on-pump coronary artery bypass grafting

Background

Diltiazem has been used during the perioperative period in patients undergoing coronary artery bypass grafting (CABG) to prevent arterial graft spasm. However, its long-term outcome effects remain unclear.

Methods

Patient records obtained from the Society of Thoracic Surgeons and the Geisinger Clinic electronic health records between October 2008 and October 2018 were screened. Adult patients who had isolated CABG with cardiopulmonary bypass were included. Cohorts of patients who received diltiazem (DILT) and those who did not (non-DILT) were matched by propensity scores based on age, gender, surgical year, Society of Thoracic Surgeons mortality and morbidity scores, and number of arterial grafts. Incidence rate ratios (IRRs) were estimated for DILT vs non-DILT on short-term adverse outcomes. Long-term survival over time was compared between DILT vs non-DILT using Kaplan-Meier curves.

Results

Among the 1004 patients included in the analyses, IRRs for the DILT group relative to the non-DILT group were: 30-day all-cause mortality, IRR: 2.33, 95% confidence interval (CI): 0.91-5.96, P=0.07; postoperative myocardial ischaemia, IRR: 1.10, 95% CI: 0.60-2.02, P=0.75; new onset atrial fibrillation, IRR: 1.06, 95% CI: 0.78-1.43, P=0.73; stroke/transient ischaemic attack, IRR: 0.76, 95% CI: 0.17-3.38, P=0.71. For long-term survival, Kaplan-Meier curves stratified by diltiazem revealed no differences in survival rates between DILT and non-DILT groups.

Conclusion

For patients undergoing on-pump CABG, perioperative diltiazem therapy did not show significant short- or long-term outcome advantages over those who did not receive diltiazem.

Determining the thermal characteristics of breast cancer based on high-resolution infrared imaging, 3D breast scans, and magnetic resonance imaging

For over the three decades, various researchers have aimed to construct a thermal (or bioheat) model of breast cancer, but these models have mostly lacked clinical data. The present study developed a computational thermal model of breast cancer based on high-resolution infrared (IR) images, real three-dimensional (3D) breast surface geometries, and internal tumor definition of a female subject histologically diagnosed with breast cancer. A state-of-the-art IR camera recorded IR images of the subject’s breasts, a 3D scanner recorded surface geometries, and standard diagnostic imaging procedures provided tumor sizes and spatial locations within the breast. The study estimated the thermal characteristics of the subject’s triple negative breast cancer by calibrating the model to the subject’s clinical data. Constrained by empirical blood perfusion rates, metabolic heat generation rates reached as high as 2.0E04 W/m³ for normal breast tissue and ranged between 1.0E05–1.2E06 W/m³ for cancerous breast tissue. Results were specific to the subject’s unique breast cancer molecular subtype, stage, and lesion size and may be applicable to similar aggressive cases. Prior modeling efforts are briefly surveyed, clinical data collected are presented, and finally thermal modeling results are presented and discussed.

Perioperative diltiazem or nitroglycerin in on-pump coronary artery bypass: A systematic review and network meta-analysis

Background

Arterial graft spasm is a severe complication after coronary artery bypass graft (CABG). Among numerous potential antispasmodic agents, systemic application of diltiazem and nitroglycerin had been investigated most frequently over the past three decades. However, it remains inconclusive if either or both agents could improve patient outcomes by preventing graft spasm when applied perioperatively, and, if so, which one would be a better choice. The current systematic review and network meta-analysis aims to summarize the data from all available randomized clinical trials of perioperative continuous intravenous infusion of diltiazem and/or nitroglycerin in patients undergoing on-pump CABG in order to define and compare their roles in graft spasm prevention and their impacts on perioperative outcomes.

Methods

We searched Ovid Medline, PubMed, CINAHL, Google Scholar and Cochrane Center for randomized controlled trials that reported outcome effects of perioperative continuous intravenous infusion of diltiazem and/or nitroglycerin in patients undergoing elective on-pump CABG. Conventional meta-analyses were conducted to evaluate the pairwise comparisons (diltiazem vs. placebo; nitroglycerin vs. placebo; diltiazem vs. nitroglycerin) on perioperative outcomes. Network meta-analyses were implemented to compare the three regimens through direct and indirect comparison.

Results

Twenty-seven studies involving 1,660 patients were included. Pairwise and network meta-analyses found no significant difference in mortality among the groups. There are four studies that reported blood flow measurements of internal mammary artery grafts intraoperatively after dissecting or immediately after distal anastomosis while patients were on continuous intravenous infusion of diltiazem and nitroglycerin. Although insufficient for data synthesis, the measured results from all four studies suggest that both diltiazem and nitroglycerin significantly increased blood flow of arterial grafts compared to placebo. For other perioperative outcomes, compared to diltiazem, patients that received nitroglycerin had higher odds of postoperative atrial fibrillation (OR = 2.67, 95% CI: 1.15 to 6.24) and higher peak serum cardiac enzymes. Patients that received placebo had higher odds of atrial fibrillation (OR = 3.00, 95% CI: 1.18 to 7.63) and lower odds of requiring inotrope support (OR = 0.19, 95% CI: 0.04 to 0.73) compared to diltiazem. Data from the network meta-analysis indicated that diltiazem had significantly lower odds of postoperative atrial fibrillation compared to nitroglycerin (OR = 0.39, 95% CI: 0.18 to 0.85). In fact, the rank from highest to lowest rates of postoperative atrial fibrillation was placebo>nitroglycerin>diltiazem. The rank from highest to lowest odds of requiring inotropic support is nitroglycerin> diltiazem>placebo. However, placebo had significantly higher odds of postoperative myocardial infarction than diltiazem (OR = 4.51, 95% CI: 1.34 to 15.25). The rank from highest to lowest odds of postoperative myocardial infarction, transient cardiac ischemic event and atrial fibrillation is placebo>nitroglycerin>diltiazem.

Conclusion

Compared to nitroglycerin and placebo, perioperative continuous intravenous infusion of diltiazem had stronger protective effects against postoperative ischemic cardiac injuries and atrial fibrillation although patients may need more inotropic support. The increased blood flow from diltiazem use in arterial grafts may potentially contribute to the drug’s outcome benefits.

Effects of intraoperative diltiazem infusion on flow changes in arterial and venous grafts in coronary artery bypass graft surgery

Objective

This study aimed to show the effects of intra-operative diltiazem infusion on flow in arterial and venous grafts in coronary artery bypass graft surgery.

Methods

Hundred fourty patients with a total of 361 grafts [205 (57%) arterial and 156 (43%) venous] underwent isolated coronary surgery. All the grafts were measured by intraoperative transit time flow meter intra-operatively. Group A (n=70) consisted of patients who received diltiazem infusion (dose of 2.5 microgram/kg/min), and Group B (n=70) didn't receive diltiazem infusion.

Results

Mean graft flow values of left internal mammary artery were 53 ml/min in Group A and 40 ml/min in Group B (P<0.001). Pulsatility index (PI) values of left internal mammary artery for Group A and Group B were 2.6 and 3.0 respectively (P<0.001). No statistically significant difference was found between venous graft parameters.

Conclusion

We recommend an effect of diltiazem infusion in increasing graft flows in coronary artery bypass graft operations.

Prevention of arterial graft spasm in rats using a vasodilator-eluting biodegradable nano-scaled fibre

OBJECTIVES

Arterial graft spasm occasionally causes circulatory collapse immediately following coronary artery bypass graft. The aim of this study is to evaluate the efficacy of our developed materials, which were composed of milrinone (phosphodiesterase III inhibitor) or diltiazem (calcium-channel blocker), with nano-scaled fibre made of biodegradable polymer to prevent arterial spasm.

METHODS

Milrinone- or diltiazem-releasing biodegradable nano-scaled fibres were fabricated by an electrospinning procedure. In vivo milrinone- or diltiazem-releasing tests were performed to confirm the sustained release of the drugs. An in vivo arterial spasm model was established by subcutaneous injection of noradrenalin around the rat femoral artery. Rats were randomly divided into four groups as follows: those that received 5 mg of milrinone-releasing biodegradable nano-scaled fibre (group M, n = 14); 5 mg of diltiazem-releasing biodegradable nano-scaled fibre (group D, n = 12); or those that received fibre without drugs (as a control; group C, n = 14) implanted into the rat femoral artery. In the fourth group, sham operation was performed (group S, n = 10). One day after the implantation, noradrenalin was injected in all groups. The femoral arterial blood flow was measured continuously before and after noradrenalin injection. The maximum blood flow before noradrenalin injection and minimum blood flow after noradrenalin injection were measured.

RESULTS

In vivo drug-releasing test revealed that milrinone-releasing biodegradable nano-scaled fibre released 78% of milrinone and diltiazem-releasing biodegradable nano-scaled fibre released 50% diltiazem on the first day. The ratios of rat femoral artery blood flow after/before noradrenalin injection in groups M (0.74 ± 0.16) and D (0.72 ± 0.05) were significantly higher than those of groups C (0.54 ± 0.09) and S (0.55 ± 0.16) (P < 0.05).

CONCLUSION

Noradrenalin-induced rat femoral artery spasm was inhibited by the implantation of milrinone-releasing biodegradable nano-scaled fibre or diltiazem-releasing biodegradable nano-scaled fibre. These results suggested that our materials might be effective for the prevention of arterial graft spasm after coronary artery bypass graft.

Dual actions of cilnidipine in human internal thoracic artery: inhibition of calcium channels and enhancement of endothelial nitric oxide synthase

OBJECTIVE

Cilnidipine is a novel, long-action L/N-type dihydropyridine calcium channel blocker that has recently been used for antihypertensive therapy. We investigated the vasorelaxation effect of cilnidipine with regard to its calcium channel blockage and nitric oxide-cyclic guanosine monophosphate-dependent mechanism in human internal thoracic artery.

METHODS

Fresh human internal thoracic arteries taken from discarded tissues of patients undergoing coronary artery bypass surgery were studied. Concentration-relaxation curves for cilnidipine in comparison with nifedipine were studied. The expression level of endothelial nitric oxide synthase mRNA was assayed by quantitative real-time polymerase chain reaction, and the phosphorylation of endothelial nitric oxide synthase at Ser(1177) was determined by Western blotting analysis.

RESULTS

Cilnidipine and nifedipine caused nearly full relaxation in potassium-precontracted internal thoracic artery. Pretreatment with cilnidipine at the clinical plasma concentration significantly depressed the maximal contraction. Endothelium denudation (47.7% ± 7.0%, P < .05) and inhibition of endothelial nitric oxide synthase (48.6% ± 6.1%, P < .05) or guanylate cyclase (41.6% ± 3.8%, P < .01) significantly reduced the cilnidipine-induced endothelium-dependent relaxation (73.9% ± 6.4%). Cilnidipine increased the expression of endothelial nitric oxide synthase mRNA by 42.4% (P < .05) and enhanced phosphorylation level of endothelial nitric oxide synthase at Ser(1177) by 37.0% (P < .05).

CONCLUSIONS

The new generation of calcium channel antagonist cilnidipine relaxes human arteries through calcium channel antagonism and increases production of nitric oxide by enhancement of endothelial nitric oxide synthase. The dual mechanisms of cilnidipine in human arteries demonstrated in this study may prove particularly important in vasorelaxing therapy in cardiovascular diseases.

Vasorelaxing effect of levosimendan against 5-hydroxytryptamine-induced contractions in isolated human conduit bypass grafts

Levosimendan is a novel inodilator drug developed for the treatment of heart failure. The possible vasodilating property of the drug in human coronary artery bypass grafts was investigated. Isometric tensions of the left internal thoracic artery (LITA, n = 8) as well as the proximal and distal segments of the radial artery (RA, n = 8 and 8) were measured in isolated organ baths. Concentration-relaxation curves for levosimendan (0.009-1.14 μmol L−1) were obtained against 5-hydroxytryptamine (5-HT; serotonin, 0.002–9.3 μmol L 1)-induced contractions. 5-HT-induced contraction of LITA was considerably smaller than that of the proximal and distal RAs. Levosimendan relaxed the grafts in the following order of calculated maximum efficacies (Emax): LITA &gt; proximal RA &gt; distal RA (LITA 100.3 ±16.2% of 5-HT-induced maximum tension, proximal RA 86.9 ±8.6%, distal RA 59.4 ± 17.5%, P &lt; 0.05 LITA vs distal RA). The potency values of levosimendan, expressed as the negative logarithm of 50% effective concentrations (pD2), were comparable in the three bypass grafts (LITA −6.52 ± 0.44 log mol L−1, proximal RA −6.60 ± 0.49 log mol L−1, distal RA −6.85 ± 0.45 log mol L−1). The results suggest that levosimendan is an effective vasorelaxant of conduit bypass grafts and may serve as a new therapeutic tool, especially in the case of LITA and proximal RA grafts, for relieving perioperative spasm and subsequent graft failure.