P6172Management of silent myocardial ischemia in patients with peripheral arterial disease needing surgery

Background

Patients with peripheral arterial disease (PAD) needing surgery have increased risk for post-operative myocardial infarction (MI)/death due to coexisting coronary artery disease (CAD). Coronary CT angiography (CTA)-derived fractional flow reserve (FFRCT) can reliably identify ischemia-producing coronary stenosis in patients with suspected CAD but its value in PAD patients is unknown.

Purpose

To determine the prevalence of silent coronary ischemia in PAD patients undergoing surgery and to assess the value of FFRCT in guiding management of patients with multisite arterial ischemia.

Methods

Patients admitted for elective carotid, aortic or peripheral vascular surgery with no cardiac history or CAD symptoms were enrolled in a prospective, open-label, ethics committee-approved study and underwent pre-op CTA and FFRCT evaluation with results available to treating physicians. Ischemia-producing coronary stenosis was defined as FFRCT≤0.80 distal to stenosis in >2mm diameter vessels. Patient management was guided by a multidisciplinary team of cardiologists, cardiovascular surgeons and anaesthesiologists. Primary endpoint was major adverse cardiac events (MACE= cardiac death, MI, urgent revasc) at 30 days with follow up at 3,6,12 months.

Results

Coronary CTA and FFRCT analysis was performed in 179 consecutive patients (age 66±8 years, male 78%, hypertension 79%, diabetes 10%, dyslipidemia 31%, smoking 37%). CTA revealed extensive coronary calcification (Agatston score 995±1004, range 0–4810) and ≥50% stenosis in 64% of patients. Ischemic coronary stenosis (FFRCT≤0.80) was present in 114 patients (64%) with FFRCT ≤0.75 in 97 (54%) and multivessel ischemia in 63 (35%). Clinically indicated vascular surgery was performed as planned in 170/179 patients (95%) with cardiac anaesthesia and close monitoring and postponed in 9 patients for coronary revascularization (3) or medical/other therapy (6). There were no post-op cardiac complications. Elective coronary angiography, performed 1–3 months post surgery in 86 patients with left main, severe or multivessel ischemia, confirmed significant stenosis in each patient with revascularization in 58 patients (53 PCI and 5 CABG) including 8 for LM disease. There have been no cardiovascular deaths; 3 patients have died of lung cancer which was first discovered on CTA. One patient had peri-procedural MI at time of PCI and one had MI and urgent PCI at 6 months. MACE at 30 days=0/179, 3 months = 1/154, 6 months=2/123, 12 months=0/65.

Conclusions

Patients undergoing elective PAD surgery have a high prevalence (64%) of unsuspected ischemia-producing coronary stenosis. Pre-op diagnosis with CTA- FFRCT can help guide a multidisciplinary team approach with optimum medical management and staged peripheral and coronary revascularization. Favourable early results are promising and suggest the need for prospective controlled studies to define the role of coronary revascularization in PAD patients.

Acknowledgement/Funding

Heartflow, Inc.; Mikrotikls Ltd

Loop diuretics decrease the renal elimination rate and increase the plasma levels of trimethylamine-N-oxide

AIMS

Trimethylamine-N-oxide (TMAO) is a novel cardiovascular risk marker. We explored the association of commonly used cardiovascular medications with TMAO levels in patients and validated the identified associations in mice.

METHODS

Detailed history of drug treatment was recorded in 300 patients with cardiovascular disease without diabetes in an observational, cross-sectional study. Animal study was performed in CD1 mice.

RESULTS

Median plasma TMAO (interquartile range) level was 2.144 (1.570-3.104) μmol l^-1 . Among nine cardiovascular drug groups, the use of loop diuretics (0.510 ± 0.296 in users vs. 0.336 ± 0.272 in nonusers, P = 0.008) and mineralocorticoid receptor antagonists (0.482 ± 0.293 in users vs. 0.334 ± 0.272 in nonusers, P = 0.007) was associated with increased log-TMAO. Acute concomitant administration of furosemide or torasemide with TMAO in mice significantly influenced TMAO pharmacokinetic profile and almost doubled the plasma TMAO area under the curve. Furosemide decreased the TMAO excretion rate by 1.9-fold during the first 30 min after administration and increased TMAO concentrations in kidney, heart and liver, suggesting the interaction of furosemide and TMAO with efflux transporters. The concentrations of TMAO in blood plasma after the administration of the organic anion transporter inhibitor probenecid were not different from those of the control group, suggesting an effect not mediated by organic anion transporters.

CONCLUSIONS

Loop diuretics increased plasma TMAO concentration by decreasing its urinary excretion rate. Loop diuretic use should be considered a potential confounder in TMAO studies.

Diabetes is Associated with Higher Trimethylamine N-oxide Plasma Levels

Recent studies have revealed strong associations between systemic trimethylamine N-oxide (TMAO) levels, atherosclerosis and cardiovascular risk. In addition, plasma L-carnitine levels in patients with high TMAO concentrations predicted an increased risk for cardiovascular disease and incident major adverse cardiac events. The aim of the present study was to investigate the relation between TMAO and L-carnitine plasma levels and diabetes. Blood plasma samples were collected from 12 and 20 weeks old db/db mice and patients undergoing percutaneous coronary intervention. Diabetic compared to non-diabetic db/L mice presented 10-fold higher TMAO, but lower L-carnitine plasma concentrations at 12 weeks of age. After 8 weeks of observation, diabetic db/db mice had significantly increased body weight, insulin resistance and TMAO concentration in comparison to non-diabetic control. In 191 patients undergoing percutaneous coronary intervention the median (interquartile range) plasma concentration of TMAO was 1.8 (1.2-2.6) µmol/L. Analysis of the samples showed a bivariate association of TMAO level with age, total cholesterol and L-carnitine. The multivariate linear regression analysis revealed that, in addition to L-carnitine as the strongest predictor of log transformed TMAO (p<0.001), the parameters of age, diabetes status and body mass index (BMI) were independently associated with increased log transformed TMAO levels (p<0.01).Our data provide evidence that age, diabetes and BMI are associated with higher TMAO levels independently of L-carnitine. These data support the hypothesis of TMAO as a cardiovascular risk marker and warrant further investigation of TMAO for diabetes research applications.

Common haplotype of interleukin-6 gene is associated with chronic total occlusions of coronary arteries

AIM

Genetic polymorphisms in genes coding for cytokines may predispose patients to coronary artery disease and chronic total occlusion (CTO) of coronary arteries. The aim of the study was to evaluate association of common genetic variations of interleukins (IL) with CTOs.

METHODS

We reviewed coronary angiograms and evaluated presence of CTOs in 684 consecutive patients with no history of revascularization. The following genetic variations were analyzed: IL-1B +3954 C>T, IL-1B -511 C>T, IL-1RN VNTR and haplotypes of IL-6 encompassing IL-6 -596 G>A, IL-6 -572 G>C, IL-6 -373 AnTn and IL-6 -174 G>C polymorphisms.

RESULTS

In 254 patients (37.1%) CTO of at least one artery was found. We observed nine IL-6 haplotypes, of which five were common (>1%) and one (GG9/12G, n=8) was not previously reported in literature. The most prevalent IL-6 haplotype (AG8/12C or Hap*1, 49.5%) correlated with CTOs, that were present in 31.5%, 36.5% and 44.5% of patients with none, one and two Hap*1, respectively (OR [95%CI] 1.252 [0.844-1.856] and 1.746 [1.104-2.762] for heterozygots and homozygots, respectively). In multivariate analysis this association became non-significant (OR [95%CI] 1.202 [0.805-1.796] and 1.529 [0.955-2.450]). In subgroup analysis Hap*1 was, however, associated with CTOs in the left anterior descending artery (p for trend 0.032) and the left circumflex artery (P=0.047), but not in the right coronary artery (p=0.799). In multivariate analysis CTOs of the left coronary arteries were associated only with total cholesterol (OR [95%CI] 1.170 [1.020-1.341]) and Hap*1 (OR [95%CI] 1.469 [0.914-2.361] and 1.970 [1.151-3.372] for heterozyogots and homozygots, respectively).

CONCLUSION

Our study suggests that common IL-6 haplotype (AG8/12C or Hap*1) is associated with development of CTOs in left coronary arteries.

C-reactive protein levels and common polymorphisms of the interleukin-1 gene cluster and interleukin-6 gene in patients with coronary heart disease

C-reactive protein (CRP) is an inflammatory marker associated with increased cardiovascular risk. Production of CRP is regulated by interleukin (IL)-1beta, IL-1 receptor antagonist and IL-6. In 160 patients with coronary heart disease (CHD) confirmed by angiography, we examined the relationship between CRP level and five polymorphisms in genes coding for these cytokines: IL-1B(-511), IL-1B(+3954), a variable number tandem repeat (VNTR) polymorphism in intron 2 of IL-1RN [IL-1RN(VNTR)], IL-6(-174) and IL-6(-572). CRP values were logarithmically normalized (log-CRP) for statistical calculations. In univariate analysis, carrier status for the IL-1B(+3954)T allele and IL-1RN(VNTR) allele 2 [IL-1RN(VNTR)*2] correlated with higher (P < 0.01) and lower (P < 0.05) log-CRP values, respectively. Among the potential confounding factors analysed, smoking, body mass index, total cholesterol (P < 0.05 for all) and diabetes (P = 0.056) were positively correlated with CRP level. After adjustment for non-genetic covariates, CRP levels remained significantly (P < 0.01) higher in carriers of IL-1B(+3954)T than in non-carriers: mean log-CRP (with 95% confidence interval) was 0.443 (0.311-0.574) for CT or TT genotypes compared with 0.240 (0.107-0.373) for the CC genotype, which corresponded to back-transformed CRP levels of 2.77 and 1.74 mg l(-1), respectively. Adjusted association was also significant for IL-1RN(VNTR)*2 (P < 0.01), with lower CRP levels in the presence of allele 2: the mean log-CRP value was 0.252 (0.115-0.388) for carriers and 0.421 (0.290-0.552) for non-carriers (CRP 1.79 and 2.64 mg l(-1), respectively). When alleles of both polymorphisms were entered into the model simultaneously, the association remained significant for IL-1B(+3954)T (P < 0.05), but not for IL-1RN(VNTR)*2. We conclude that IL-1B(+3954)T is associated with higher CRP levels in patients with CHD, and we found that this association was significant after adjustment for major risk factors. Our data also suggest a possible relationship of IL-1RN(VNTR)*2 with lower CRP levels in the same patients.