Comparison of response to serotonin of radial artery grafts and internal mammary grafts to native coronary arteries and the effect of diltiazem

Management of severe arterial hypertension associated with serotonin syndrome: a case report analysis based on systematic review techniques

Serotonin syndrome is thought to arise from serotonin excess. In many cases, symptoms are mild and self-limiting. But serotonin syndrome can become life threatening, when neuromuscular hyperexcitability spins out of control. Uncontainable neuromuscular hyperexcitability may lead to cardiovascular complications, linked to extreme changes in blood pressure. Currently, there is little guidance on how to control blood pressure in hyperserotonergic states. We report a case with treatment-resistant arterial hypertension, followed by a clinical review (using systematic review principles and techniques) of the available evidence from case reports published between 2004 and 2016 to identify measures to control arterial hypertension associated with serotonin syndrome. We conclude that classic antihypertensives may not be effective for the treatment of severe hypertension associated with serotonin syndrome. Benzodiazepines may lower blood pressure. Patients with severe hypertension not responding to benzodiazepines may benefit from cyproheptadine, propofol or both. In severe cases, higher cyproheptadine doses than currently recommended may be necessary.

Comparison of the radial artery and saphenous vein as composite grafts in off-pump coronary artery bypass grafting in elderly patients: a randomized controlled trial

Background and Objectives

Arterial grafts have a better long-term patency rate than saphenous vein (SV) when used in off-pump coronary artery bypass surgery (OPCAB). However, arterial grafts in elderly patients are often diseased. We sought to compare the early outcomes achieved by using the two different types of composite grafts.

Subjects and Methods

We conducted a randomized trial to compare radial artery (RA) and SV composite grafts based on the in situ left internal mammary artery in 60 elderly (>70 years old) patients, who were scheduled to undergo OPCAB. Clinical outcomes and 1-year postoperative CT angiography results were compared. The quality of the conduit was evaluated by employing vascular ultrasonography, optical coherence tomography (OCT), and histologic examination.

Results

No differences in immediate postoperative morbidity and mortality were observed between the two groups. Early postoperative CT angiography revealed a SV patency rate of 100%, which was not different from that of RA composite grafts (99.1%). CT angiography after a year showed an overall patency rate of 96.3%. The overall patency rate of the SV group at 1 year was 94.7%, which was similar to that of the RA group (97.4%). Also, there was no difference in overall survival rate between the two groups. Vascular ultrasonographic images showed strong correlations between OCT and histopathology.

Conclusion

Our analysis of early outcomes revealed that the SV could be used as an alternative composite graft to the RA in elderly patients. Vascular ultrasonography is an accurate, real-time, and reproducible method for assessing the quality of the RA conduit.

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 > proximal RA > 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 < 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.

Atherosclerosis of Radial and Internal Thoracic Arteries Used in Coronary Bypass: Atherosclerosis in Arterial Grafts

BACKGROUND

This study aimed to evaluate the degree and incidence of atherosclerosis in internal thoracic (ITA) and radial arteries (RA) harvested for coronary bypass grafting.

MATERIALS AND METHODS

The association of major clinical events and etiological factors for atherosclerosis was investigated in 770 arterial segments obtained prospectively from 480 patients. Potential risk factors for atherosclerosis were age, gender, smoking, diabetes mellitus, peripheral vascular disease, cerebrovascular disease, chronic renal failure, hypercholesterolemia, obesity, hypertension, and a positive family history.

RESULTS

Six types of histological lesions have been defined; grade III or more was present in the RA in 47 (16%) patients and in the ITA in 30 (7%). The mean grade was 1.6 +/- 0.6 in the ITA and 2.1 +/- 0.9 in the RA (p < 0.001).

CONCLUSION

RA had a significantly greater prevalence of atherosclerosis than the same patients' ITA. There was a strong correlation between ITA atherosclerosis and age. The presence of calcification may lead surgeons to avoid an extra incision according to risk factors, although most of these are not predictive.

Radial Artery Graft for Coronary Artery Bypass Surgery: Biological Characteristics and Clinical Outcome

The radial artery (RA) is gaining popularity as a bypass conduit for coronary artery bypass grafting, and its impact on clinical practice has been extensively explored. In the present article, we provide a review of postoperative hand circulation, vascular biological characteristics of the RA graft, the efficacy of vasodilator therapies, and mid-term clinical results of use of the RA graft. Fundamental studies revealed excellent vascular biological characteristics of the RA graft as a living arterial conduit, making it almost equivalent to the internal thoracic artery (ITA) graft. Clinical studies have yielded encouraging mid-term results. Most studies reported in favor of the RA graft over the saphenous vein graft with regard to patency rate, freedom from cardiac events, and survival. However, superiority of either the RA or right ITA graft has not been conclusively determined. The long-term results of RA grafts remain unknown, but at present, supplementary use of an RA graft with a left ITA graft appears feasible for CABG.

Increased incidence of radial artery calcification in patients with diabetes mellitus

BACKGROUND

The radial artery (RA) has become a popular conduit for coronary artery bypass (CAB). Preoperative RA evaluation in CAB patients has focused on ulnar collateral circulation to the hand and not on the conduit itself, yet the RA is prone to atherosclerosis and perhaps calcification, particularly in patients with diabetes mellitus (DM). We sought to determine the incidence of RA calcific disease in diabetic vs nondiabetic patients using ultrasonography to establish its role in preoperative evaluation of CAB patients.

METHODS

Ultrasound images of the RA were obtained in 102 men (49 with DM) referred to a vascular laboratory. For each patient, a RA calcification index (CI; 0-4) was derived from separate scores accounting for calcification density, longitudinal vessel involvement, and bilaterality. Differences between diabetic and nondiabetic patients were determined by unpaired t test.

RESULTS

Mean (+/-SEM) CI was greater in diabetic patients vs nondiabetics (2.32 +/- 0.21 vs 1.17 +/- 0.20; P < 0.0001), due mainly to an increase in dense calcification, which was observed in 17 (34%) diabetics vs 5 (9.6%) nondiabetics (P = 0.007). Calcifications were completely absent in 27 (52%) nondiabetics vs 9 (18%) diabetics (P = 0.000).

CONCLUSIONS

These data indicate that both the incidence and the severity of RA calcific disease are increased by DM. Preoperative imaging of the RA should be considered in diabetic CAB candidates and perhaps in nondiabetics with multiple risk factors to avoid unnecessary forearm exploration or inadvertent use of a diseased conduit.

Sarpogrelate inhibits serotonin-induced proliferation of porcine coronary artery smooth muscle cells: implications for long-term graft patency

BACKGROUND

Serotonin can induce proliferation of vascular smooth muscle cells. We assessed the ability of a specific serotonin receptor antagonist, sarpogrelate, to inhibit proliferation of cultured porcine coronary artery smooth muscle cells.

METHODS

Cell proliferation and mitotic activity were measured using 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyltetrazolium bromide. To determine the effect of sarpogrelate on DNA (deoxyribonucleic acid), RNA (ribonucleic acid), and protein synthesis, radioactive incorporation of 3H-thymidine, 3H-uridine, and 3H-phenylalanine, respectively, was used. Synthesis of DNA was also assessed by flow cytometry with propidium iodide as a fluorochrome.

RESULTS

Serotonin, platelet-derived growth factor, endothelin, and angiotensin II all induced proliferation of porcine coronary artery smooth muscle cells. Sarpogrelate specifically inhibited the serotonin-induced cytokine trigger but did not influence platelet-derived growth factor-, endothelin-, or angiotensin II-induced cell proliferation. Sarpogrelate inhibited the serotonin-induced increase in intracellular free ionized calcium concentration, prevented mitogen-activated protein kinase activation, and down-regulated expression of the protooncogenes c-fos and c-jun. Sarpogrelate acted at the G1 phase of the cell cycle.

CONCLUSIONS

These data suggest that sarpogrelate could be used as a therapeutic agent to inhibit serotonin-induced neointimal hyperplasia and improve patency of coronary artery bypass grafts.

Calcium-channel antagonists and nitrates in coronary artery bypass patients receiving radial artery grafts

OBJECTIVE

To review the literature assessing the role of vasodilators for the prevention of vasospasm leading to graft failure in patients receiving the radial artery (RA) as a conduit in coronary artery bypass grafting (CABG).

DATA SOURCE

A MEDLINE search (January 1966-May 2000) was performed using calcium-channel antagonists, nitrates, radial artery, and coronary artery bypass as key words. English-language articles were identified, and the references of these articles were used to further identify pertinent articles.

DATA SYNTHESIS

RAs can be used as conduits in CABG. It has been suggested that failure of these grafts may be due to vasospasm, leading to occlusion observed angiographically. Calcium-channel antagonists and nitrates have been proposed as a means of preventing vasospasm and subsequent graft failure.

CONCLUSIONS

Currently published data on the use of calcium-channel antagonist or nitrate therapy as prophylaxis against vasospasm in patients receiving RA grafts are inconclusive. Systematic evaluations of currently available pharmacologic agents are needed to guide clinical practice in this area.

Prevention of radial artery graft vasospasm after coronary bypass

BACKGROUND

Pharmacologic prophylaxis for prevention of notorious radial artery (RA) spasm is critical because of the increasingly routine use of the RA conduit during coronary bypass. Therefore, we investigated the vasodilatory effect of calcium antagonist in combination with nitroglycerin (NTG) RA segments.

METHODS

We evaluated the vasodilatory effect of nifedipine alone, verapamil alone, diltiazem alone, NTG alone, and calcium antagonist in combination with in endothelin-1 (ET-1)-, angiotensin II (AII)-, 5-hydroxytryptamine (5-HT)-, and norepinephrine (NE)-precontracted human RA rings mounted in organ baths.

RESULTS

Nifedipine (10(-5) M) alone, diltiazem (10(-5) M) alone, verapamil (10(-5) M) alone, and NTG (10(-5) M) alone showed maximum vasodilatory effect in either 10(-7) M ET-1-, 10(-7) M AII-, 10(-5) M NE-, or 10(-4) M 5-HT-precontracted RA segments. The 10(-5) M NTG alone-induced vasodilation (88.5% +/- 7.7%) in ET-1-precontracted segments was the highest vasodilation (ANOVA, p = 0.0008) among NTG alone-induced vasodilatory effects in RA. The relaxing effect of any of the calcium antagonists alone varied from 32.7% +/- 13.2% to 76.5% +/- 20.5% in RA precontracted with different vasoconstrictors. Nearly 200% vasodilation was observed with calcium antagonist in combination with NTG in AII-precontracted vessels. Nonetheless, the vasodilatory effect of calcium antagonist in combination with NTG in RA segments precontracted with different vasoconstrictors other than AII was nearly 100%.

CONCLUSIONS

A calcium antagonist in combination with NTG is more potent than calcium antagonist alone or NTG alone in prevention of human RA vasospasm after coronary bypass.

Nitroglycerin is preferable to diltiazem for prevention of coronary bypass conduit spasm

BACKGROUND

Diltiazem is widely used to prevent radial artery spasm after coronary bypass grafting (CABG). However, recent in vitro and in vivo studies have shown that nitroglycerin is a superior conduit vasodilator compared to diltiazem. A clinical comparison of these agents in patients undergoing CABG has not been previously performed.

METHODS

One hundred sixty-one consecutive patients undergoing isolated CABG with the radial artery were prospectively randomized to 24-hour intravenous infusion of nitroglycerin or diltiazem followed by 6-month treatment with a daily dose of isosorbide mononitrate (n = 84) or diltiazem CD (n = 77). Analyses were performed on "intention-to-treat" basis.

RESULTS

Crossovers because of low cardiac output, complete heart block, or sinus bradycardia occurred in 5 patients in the diltiazem group and none in the nitroglycerin group (p = 0.05). Operative mortality (nitroglycerin, 1.2% versus diltiazem, 1.3%), major morbidity (14% versus 16%), perioperative myocardial infarction (1.2% versus 0%), peak serum creatinine phosphokinase MB fraction levels (27 versus 21 U), intensive care unit stay (34+/-19 versus 38+/-30 hours) and total hospital length of stay (4.7+/-1.4 versus 4.7+/-1.3 days) were similar (p = not significant for all). Cardiac pacing was required more often in the diltiazem group (28% versus 13%, p = 0.01). Follow-up longer than 2 months was available in 145 patients (90%). Follow-up mortality (nitroglycerin, 1.2%; diltiazem, 1.3%), myocardial infarction (6%, versus 5%), and reintervention (8% versus 6%) rates and average angina class (1.3+/-0.7 versus 1.1+/-0.4) were similar (p = not significant for all). Thallium stress test obtained in 117 patients showed abnormal perfusion in the radial artery territory in only 4 patients (3%), 2 in each group (p = not significant). Treatment with diltiazem was more costly ($16,340 versus $1,096).

CONCLUSIONS

Nitroglycerin is preferable to diltiazem for prevention of conduit spasm. Nitroglycerin is safe, effective, better tolerated, and less costly than diltiazem, and therefore, should be the agent of choice.