Does isolated myocardial bridge really interfere with coronary blood flow?

BackgroundMyocardial bridge (MB) is defined as a segment of a major epicardial coronary artery the “tunneled artery” that goes intramurally through the myocardium beneath the muscle bridge. Multiple methods have been proposed to assess coronary flow rate among which thrombolysis in acute myocardial infarction frame count was a relatively new semiquantitative method.ObjectivesOur goal was to determine incidence of MB in the patients undergoing coronary angiography in Mansoura Specialized Hospital, Cardiac Catheterization Laboratory, also to investigate the hypothesis that slow coronary flow rate may be linked to angina or angina like symptoms in patients with MB without stenotic lesions in epicardial coronary arteries using TFC.Patients and methodsFifteen patients with MB (group I) were retrospectively collected from Mansoura Specialized Hospital, Cardiac Catheterization Laboratory, we review 3000 cases referred to diagnostic coronary angiography to exclude significant coronary artery disease. Fifteen patients with normal coronary angiography served as control (group II). We review the clinical presentations, risk factors, echocardiographic data for both test and control groups. TFC was calculated using a simple continuous index.ResultsThe incidence of MB in our study was 0.5%. CTFC in LAD was significantly higher in the patients with MB compared with control. No significant correlation between TFC and echocardiographic parameters.ConclusionsMyocardial bridging must be considered especially in patients at low risk for coronary atherosclerosis but with angina like chest pain or established myocardial ischemia. We suggest that coronary blood flow is decreased in the patients with MB compared with the patients having normal coronary.     

Do beta-adrenergic blocking agents increase coronary flow reserve?

BACKGROUND

Beta-adrenergic blocking agents are the cornerstone in the treatment of coronary artery disease (CAD). The exact pathophysiologic mechanism is not clear but depends largely on the oxygen-sparing effect of the drug. Thus, the effect of metoprolol on coronary flow reserve and coronary flow velocity reserve (CFVR) was determined in patients with CAD.

METHODS

Coronary blood flow velocity was measured with the Doppler flow wire in 23 patients (age: 56 ± 10) undergoing percutaneous transluminal coronary angioplasty for therapeutic reasons. Measurements were carried out at rest, after 1-min vessel occlusion (postischemic CFVR) as well as after intracoronary adenosine (pharmacologic CFVR) before and after 5 mg intravenous metoprolol. In a subgroup (n = 15), absolute flow was measured from coronary flow velocity multiplied by coronary cross-sectional area.

RESULTS

Rate-pressure product decreased after metoprolol from 9.1 to 8.0 × 10³ mm Hg/min (p < 0.001). Pharmacologic CFVR was 2.1 at rest and increased after metoprolol to 2.7 (p = 0.002). Likewise, postischemic CFVR increased from 2.6 to 3.3 (p < 0.001). Postischemic CFVR was significantly higher than pharmacologic CFVR before as well as after metoprolol. Coronary vascular resistance decreased after metoprolol from 3.4 ± 2.0 to 2.3 ± 0.7 mm Hg × s/cm (p < 0.02).

CONCLUSIONS

The following conclusions were drawn from this study. Metoprolol is associated with a significant increase in postischemic and pharmacologic CFVR. However, postischemic CFVR is significantly higher than pharmacologic CFVR. The increase in CFVR by metoprolol can be explained by a reduction in vascular resistance. The increase in CFVR (= increased supply) and the reduction in oxygen consumption (= decreased demand) after metoprolol explain the beneficial effect of this beta-blocker in patients with CAD.     

Could fractional flow reserve guide therapeutic strategy in acute coronary syndrome?

Fractional flow reserve, as determined with a pressure-wire, was validated in the assessment of the functional severity of intermediate lesions in a population with stable ischemic cardiopathy. The value of pressure-wire analysis in acute coronary syndrome is unknown. We report two patients with acute coronary syndrome, in which the therapeutic approach was guided by the fractional flow reserve. We discuss the utility of this tool in this context.     

Correlation between arterial stiffness and coronary flow velocity reserve in subjects with pulse wave velocity >1400 cm/s

Brachial-ankle pulse wave velocity (ba-PWV) is an independent predictor for cardiovascular events. Coronary flow velocity reserve (CFVR) provides important information for coronary endothelial function. In the present study, we investigated the possible relationship between PWV and CFVR, especially in subjects with PWV?>?1400?cm/s. Seventy five subjects were divided into two groups based on baPWV value (baPWV?>?1400?cm/s versus baPWV?<?1400?cm/s). PWV and CFVR were measured by Colin VP-1000 apparatus and non-invasive Doppler echocardiography, respectively. Our results showed that CFVR was significantly lower in patients with baPWV?>?1400?cm/s than in patients with baPWV?<?1400?cm/s (2.57?±?0.68 versus 3.04?±?0.73, p?<?0.01). baPWV was negatively correlated with CFVR in the entire study group (r?=??0.45, p?<?0.0001) even adjusting for age, prevalence of diabetes mellitus and systolic blood pressure (r?=??0.33, p?=?0.044). Moreover, baPWV was markedly negatively correlated with CFVR in patients with baPWV?>?1400?cm/s (r?=??0.42, p?<?0.01). Multiple linear regressions showed that baPWV was independently associated with CFVR in the entire study group (β?=??0.702, p?<?0.001). Our results showed that large arterial stiffness was negatively correlated with decreased CFVR especially in subjects with baPWV?>?1400?cm/s, and baPWV was independently associated with CFVR.     

Is the coronary flow velocity reserve improvement after aortic valve replacement for aortic stenosis transient? Results of a 3-year follow-up

The coronary flow velocity reserve (CFR) is decreased in patients with aortic valve stenosis (AS). The aim of the present prospective study was to examine the CFR in AS patients with normal epicardial coronary arteries during a 3-year follow-up of aortic valve replacement (AVR). A total of 30 AS patients (17 women and 13 men) were enrolled in this prospective follow-up study; they all had a normal coronary angiogram and underwent dipyridamole stress transesophageal echocardiography (STEE) for CFR measurement before AVR. Nine of them participated in this 3-year follow-up study, and all patients were examined 16 months and 3 years after AVR by STEE. The CFR of AS patients was decreased before AVR. Different extents of diastolic coronary flow velocity reduction (resting and posthyperaemic) were observed resulting in a significant CFR improvement, despite the low number of patients during the 16-month follow-up. A further posthyperemic flow velocity reduction was demonstrated after the 3-yearfollow-up, resulting in a significant CFR impairment. The CFR decreased in 5 cases, but remained practically unchanged in 3 after the first CFR measurement; only the CFR of 1 patient improved minimally. The main finding of the current study is that the CFR improvement 16 months after AVR, which paralleled the regression of the left ventricular hypertrophy, was found to be transient. Coronary flow velocity reserve impairment was demonstrated after the long-term (3-year) follow-up in most of the patients, which could not be explained by extravascular compressive forces. The topic of this paper was presented at the European Society of Cardiology Congress 2004, Munich, Germany     

Does tranexamic acid reduce blood loss in off-pump coronary artery bypass?

The hemostatic effect of tranexamic acid on the bleeding tendency and transfusion requirements in patients undergoing off-pump coronary artery bypass surgery was assessed in a prospective randomized double-blind study. Of 66 patients undergoing elective operations, 33 were given tranexamic acid (15 mg x kg(-1) before infusion of heparin and 15 mg x kg(-1) after protamine infusion), and the other 33 received only saline. Postoperative bleeding, transfusions, complications, hematological variables, and plasma D-dimer levels were recorded. Postoperative blood loss was significantly less in the tranexamic acid group compared to the control group (320 +/- 38 vs 480 +/- 75 mL). Patients in the tranexamic acid group received significantly less allogeneic blood products (0.46 vs 0.94 units per patient), and they had lower postoperative D-dimer levels. No postoperative thrombotic complications were observed in either group. Although off-pump coronary artery bypass surgery is associated with reduced frequency of hemorrhagic disorders, defective hemostasis still occurs, and tranexamic acid effectively reduces postoperative blood loss and the need for allogeneic blood products.