Angiotensin-converting enzyme genotypes and risk for myocardial infarction in women

OBJECTIVES

We tested for an association between the angiotensin-converting enzyme (ACE) DD polymorphic genotype and myocardial infarction (MI) in a sample group composed exclusively of women.

BACKGROUND

The human ACE gene occurs with either an insertion (I allele) or a deletion (D allele) of a 287-base pair (bp) Alu element. Part of the variance in serum ACE levels may be accounted for by this polymorphism. Also, the DD genotype has been associated with an increased risk of MI in predominantly male populations. However, the risk in women is poorly defined.

METHODS

Genomic DNA was extracted from buffy coat blood using a phenol/chloroform method. Angiotensin-converting enzyme alleles were identified using primers to bracket the insertion region in intron 16. Amplification using polymerase chain reaction allowed identification of a 490-bp (I allele) or a 190-bp (D allele) product, or both.

RESULTS

Allelic and genotypic frequencies in control subjects were similar to those reported in mostly male populations, and frequencies of genotypes were in the Hardy-Weinberg equilibrium. In contrast, the distribution of genotypes in patients with MI diverged from the equilibrium. Specifically, DD genotypic frequency was increased in women with (n = 141) versus without (n = 338) a previous MI (39% vs. 29%, odds ratio [OR] 1.54, 95% confidence interval 1.02 to 2.32, p < 0.04). Risk was particularly increased in women <60 years old (OR 2.04, p < 0.05). In contrast, the DD genotype did not predict angiographic coronary artery disease.

CONCLUSIONS

Consistent with findings in male-dominated populations, a modest association of the ACE DD genotype with MI was found in women. The basis for this association requires further study.

Infection with Chlamydia pneumoniae accelerates the development of atherosclerosis and treatment with azithromycin prevents it in a rabbit model

BACKGROUND

Chlamydia pneumoniae infection has been associated with atherosclerosis by serological studies and detection of bacterial antigen within plaque. We sought to evaluate a possible causal role in an animal model.

METHODS AND RESULTS

Thirty New Zealand White rabbits were given three separate intranasal inoculations of either C pneumoniae (n = 20) or saline (n = 10) at 3-week intervals and fed chow enriched with a small amount (0.25%) of cholesterol. Immediately after the final inoculation, infected and control rabbits were randomized and begun on a 7-week course of azithromycin or no therapy. Three months after the final inoculation, rabbits were euthanatized and sections of thoracic aortas were blindly evaluated microscopically for maximal intimal thickness (MIT), percentage of luminal circumference involved (PLCI), and plaque area index (PAI) of atherosclerosis. Vascular chlamydial antigen was assessed by direct immunofluorescence. MIT differed among treatment groups (P=.009), showing an increase in infected rabbits (0.55 mm; SE = 0.15 mm) compared with uninfected controls (0.16 mm; SE = 0.06 mm) and with infected rabbits receiving antibiotics (0.20 mm; SE = 0.03 mm) (both P<.025), whereas MIT in infected/treated versus control rabbits did not differ. PLCI also tended to differ (P<.1) and PAI differed significantly (P<.01) among groups with a similar pattern. Chlamydial antigen was detected in 2 untreated, 3 treated, and 0 control animals.

CONCLUSIONS

Intranasal C pneumoniae infection accelerates intimal thickening in rabbits given a modestly cholesterol-enhanced diet. In addition, weekly treatment with azithromycin after infectious exposure prevents accelerated intimal thickening. These findings strengthen the etiologic link between C pneumoniae and atherosclerosis and should stimulate additional animal and human studies, including clinical antibiotic trials.

"Rescue" utilization of abciximab for the dissolution of coronary thrombus developing as a complication of coronary angioplasty

OBJECTIVES

This study sought to test the effect on thrombus score of the "rescue" utilization of the glycoprotein IIb/IIIa antagonist abciximab given to patients in whom intracoronary thrombus has developed as a complication after percutaneous transluminal coronary angioplasty (PTCA) and to determine its clinical utility.

BACKGROUND

Abciximab is effective in the prevention of acute ischemic complications when given prophylactically to patients during high risk PTCA. However, its ability to therapeutically dissolve newly formed intracoronary thrombus occurring as a complication after PTCA is not known.

METHODS

We performed an observational study in 29 consecutive patients who received abciximab (0.25 mg/kg body weight intravenous bolus, followed by a 12-h infusion at 10 microg/min) after attempted PTCA caused either the new development or further progression of thrombus. Angiograms were analyzed to determine thrombus score and Thrombolysis in Myocardial Infarction (TIMI) flow grade before and after abciximab. Procedural and clinical success and long-term outcome were also determined.

RESULTS

Thrombus score decreased from 3.0 +/- 0.9 (mean +/- SD) to 0.86 +/- 0.92 (p < 0.001), and TIMI flow grade increased from 2.5 +/- 0.7 to 2.9 +/- 0.3 (p = 0.008). No instances of distal embolization or no-reflow were noted. The procedural success (< or = 50% residual stenosis) rate was 97%. The clinical success (procedural success with no in-hospital myocardial infarction, bypass surgery or death) rate was 93%.

CONCLUSIONS

Dissolution of thrombus and restoration of TIMI grade 3 flow were readily achieved after administration of abciximab when delivered in a "rescue" manner after the development of thrombosis after PTCA. This novel use of abciximab will need to be validated in randomized trials.

Prospective, randomized, multicenter comparison of laser-facilitated balloon angioplasty versus stand-alone balloon angioplasty in patients with obstructive coronary artery disease. The Laser Angioplasty Versus Angioplasty (LAVA) Trial Investigators

OBJECTIVES

The goal of this study was to examine the relative safety and efficacy of laser-facilitated percutaneous transluminal coronary angioplasty (PTCA) versus "stand-alone" PTCA.

BACKGROUND

Plaque debulking with lasing before PTCA may result in improved lumen dimensions and decreased rates of periprocedural ischemic complications, thus improving short- and long-term outcomes after percutaneous intervention. The mid-infrared holmium:yttrium-aluminum-garnet (YAG) laser has been shown to be effective in a variety of plaque subtypes and may be particularly useful in high risk acute ischemic syndromes.

METHODS

A total of 215 patients (mean [+/-SD] age 61 +/- 12 years) with 244 lesions were prospectively randomized at 14 clinical centers to laser versus stand-alone PTCA. After laser treatment, all patients underwent PTCA; 148 patients (69%) had unstable angina.

RESULTS

The procedural success rate without major catheterization laboratory complications was similar in patients assigned to laser treatment or PTCA alone (96.6% vs. 96.9%, p = 0.88), as was the in-hospital clinical success rate (89.7% vs. 93.9%, p = 0.27). There was no difference in postprocedural diameter stenosis after laser treatment compared with PTCA (18.3% +/- 13.6% vs. 19.5% +/- 15.1%, p = 0.50). However, use of the laser, versus PTCA alone, did result in significantly more major and minor procedural complications (18.0% vs. 3.1%, p = 0.0004), myocardial infarctions (4.3% vs. 0%, p = 0.04) and total in-hospital major adverse events (103% vs. 4.1%, p = 0.08). At a mean follow-up time of 11.2 +/- 7.7 months, there were no differences in late or event-free survival in patients assigned to laser treatment versus PTCA alone.

CONCLUSIONS

Compared with stand-alone PTCA, laser-facilitated PTCA results in a more complicated hospital course, without immediate or long-term benefits.

A comparison of the accuracy and reproducibility of digital three-dimensional coronary artery reconstructions using edge detection or videodensitometry

Global quantitative three-dimensional measurements of coronary arteries may be helpful in determining the functional significance of various forms of coronary pathology. A computerized system has been developed that is capable of performing 3-D reconstruction of digitized images obtained from multiple coronary angiographic views using either automated edge detection (AED) or videodensitometric (VD) techniques. To compare the accuracy and reproducibility of measurements obtained from this system using either technique, stationary and moving coronary aluminum 3-D phantoms, each with 13 branches (diameter 0.58-6.35 mm, length 21.5-64.5 mm), were imaged and reconstructed 10 separate times each. Individual branch lengths and diameters were calculated and compared to each other and to known values. Diameter measurements were compared using either AED or VD. Intraclass correlation coefficients between observed values (ICC) for vessel length were r = 0.89 for the stationary and r = 0.97 for the moving phantom. ICCs for vessel diameter were r = 0.93 (AED) and r = 0.95 (VD) for the stationary and r = 0.98 (AED) and r = 0.97 (VD) for the moving phantom. Mean differences (+/-SD) between true and observed values [MDTO(+/-SD)] for vessel length were -1.0 +/- 3.9 mm for the stationary and -3.5 +/- 3.2 mm for the moving phantom. MDTO(+/-SD) for vessel diameter were -0.10 +/- 0.52 mm (AED) and +0.03 +/- 0.30 mm (VD) for the stationary and -0.21 +/- 0. 44 mm (AED) and -0.12 +/- 0.33 (VD) for the moving phantom. We conclude that the quantitative accuracy and reproducibility of measurements obtained by computerized 3-D reconstruction of coronary model phantoms is of high enough quality to warrant further clinical evaluation. VD appears to be more accurate than AED for measuring vessel diameter.

A mutation in the methylenetetrahydrofolate reductase gene is not associated with increased risk for coronary artery disease or myocardial infarction

OBJECTIVES

We sought to determine whether the C677T transition in the methylenetetrahydrofolate reductase (MTHFR) gene is associated with increased risk for coronary artery disease (CAD) or myocardial infarction (MI).

BACKGROUND

Elevated plasma homocysteine has been identified as a risk factor for coronary atherosclerosis. Homocysteinemia may result from deficient MTHFR activity. A thermolabile form of MTHFR, associated with a C677T genetic transition, shows reduced activity and may be a risk factor for CAD.

METHODS

Blood was withdrawn from patients undergoing coronary angiography, and DNA was extracted by a phenol-chloroform method. Genotyping was done by polymerase chain reaction (PCR) amplification of a 198-base pair segment of the MTHFR gene that brackets nucleotide 677. The amplicon was digested with the HinfI restriction enzyme. Products were visualized after electrophoresis in 1.5% agarose with ethidium bromide.

RESULTS

Among 200 patients with a diagnosis of MI, the polymorphic allelic frequency was 33.3%, compared with 32.1% among 554 control subjects (p = 0.68); homozygosity was present in 11.5% of patients and 10.6% of control subjects (p = 0.74, odds ratio [OR] 1.09, 95% confidence interval [CI] 0.63 to 1.82). Among 510 patients with severe CAD (>60% stenosis), allelic frequency was 32.0%, compared with 34.8% for 168 subjects without CAD (<10% stenosis, p = 0.33); 11.2% of patients with CAD compared with 13.1% of control subjects were homozygous (p = 0.50, OR 0.83, 95% CI 0.5 to 1.40).

CONCLUSIONS

Patients with angiographic evidence of CAD or clinical MI do not show an increased frequency of the C677T transition in the MTHFR gene. Our findings do not support this polymorphism as a risk factor for CAD or MI in a predominantly white, well nourished population of unrestricted age.

Velocity measurement based on bolus tracking with the aid of three-dimensional reconstruction from digital subtraction angiography

The problem of blood flow measurement in x-ray angiography using measurements of the leading edge of the contrast bolus as it traverses the vascular bed is considered. A new technique for velocity measurement is presented based upon the ratio of the temporal derivative to the spatial derivative of the contrast bolus in the direction of flow. With the addition of a small correction factor, the value obtained is shown to reflect the transport velocity, or the velocity at which the contrast is transported down the vessel of interest. Most blood flow measurements based on bolus tracking techniques are actually using the contrast transport velocity to represent the blood flow velocity. Because of the streaming that occurs due to laminary flow conditions, the measured transport velocity is found to be somewhere between the average and the peak (central) fluid velocities for measurements taken during the traversal of the bolus leading edge. The spatial and temporal variation of the transport velocity are found to be consistent with the bolus motion expected in the presence of laminar flow. From x-ray images of contrast passage through simple tubes, we find that the derivative method measures the transport velocity during passage of the bolus leading edge. In most cases of laminar blood flow, the leading edge transport velocity can be 20%-40% higher than the average blood velocity.

Explaining discrepant mortality results between primary percutaneous transluminal coronary angioplasty and thrombolysis for acute myocardial infarction

Differing relative outcomes in randomized versus registry studies comparing primary angioplasty with thrombolytic therapy for acute myocardial infarction suggest a clinical paradox. A predictive model based on differences in 5 treatment-related factors, including time to therapy, patency success, and angioplasty experience, suggests that relative outcomes may indeed vary, depending on the clinical setting in which therapy is given.

An emergency department-based protocol for rapidly ruling out myocardial ischemia reduces hospital time and expense: results of a randomized study (ROMIO)

OBJECTIVES

We tested the hypothesis that an emergency department-based protocol for rapidly ruling out myocardial ischemia would reduce hospital time and expense but maintain diagnostic accuracy.

BACKGROUND

Patients with a missed diagnosis of myocardial infarction have a high mortality rate; however, providing routine hospital care to low risk patients may not be time- or cost-effective.

METHODS

One hundred low risk patients were entered into the study and randomized either to an emergency department-based rapid rule-out protocol (n = 50) or to routine hospital care (n = 50). Patients receiving routine care were managed by their attending physicians. The rapid protocol included serum enzyme testing at 0, 3, 6 and 9h, serial electrocardiograms with continuous ST segment monitoring and, if results were negative, a predischarge graded exercise test. Study patients were also compared with 160 historical control subjects.

RESULTS

Myocardial infarction or unstable angina occurred in 6% of patients within 30 days; no diagnoses were missed. By intention to treat analysis (n = 50 in each group), the hospital stay was shorter and charges were lower with the rapid protocol than with routine care (p = 0.001). Among patients in whom ischemia was ruled out, those assigned to the rapid protocol had a shorter hospital stay (median 11.9 vs. 22.8 h, p = 0.0001) and lower initial ($893 vs $1,349, p = 0.0001) and 30-day ($898 vs. $1,522, p = 0.0001) hospital charges than did patients given routine care. In historical control subjects, the hospital stay was longer (median 34.5 h, p = 0.001 vs. either group) and charges greater (median $2,063, p = 0.001, vs rapid protocol, p = 0.02, vs. routine care group).

CONCLUSIONS

In low risk patients who present to the emergency department with chest pain, the rapid protocol ruled out myocardial infarction and unstable angina more quickly and cost-effectively than did routine hospital care.

Increased incidence of Chlamydia species within the coronary arteries of patients with symptomatic atherosclerotic versus other forms of cardiovascular disease

OBJECTIVES

The objectives of this study were to test prospectively for an association between Chlamydia and atherosclerosis by comparing the incidence of the pathogen found within atherosclerotic plaques in patients undergoing directional coronary atherectomy with a variety of control specimens and comparing the clinical features between the groups.

BACKGROUND

Previous work has suggested an association between Chlamydia pneumoniae infection and coronary atherosclerosis, based on the demonstration of increased serologic titers and the detection of bacteria within atherosclerotic tissue, but this association has not yet been regarded as established.

METHODS

Coronary specimens from 90 symptomatic patients undergoing coronary atherectomy were tested for the presence of Chlamydia species using direct immunofluorescence. Control specimens from 24 subjects without atherosclerosis (12 normal coronary specimens and 12 coronary specimens from cardiac transplant recipients with subsequent transplant-induced coronary disease) were also examined.

RESULTS

Coronary atherectomy specimens were definitely positive in 66 (73%) and equivocally positive in 5 (6%), resulting in 79% of specimens showing evidence for the presence of Chlamydia species within the atherosclerotic tissue. In contrast, only 1 (4%) of 24 nonatherosclerotic coronary specimens showed any evidence of Chlamydia. The statistical significance of this difference is a p value < 0.001. Transmission electron microscopy was used to confirm the presence of appropriate organisms in three of five positive specimens. No clinical factors except the presence of a primary nonrestenotic lesion (odds ratio 3.0, p = 0.057) predicted the presence of Chlamydia.

CONCLUSIONS

This high incidence of Chlamydia only in coronary arteries diseased by atherosclerosis suggests an etiologic role for Chlamydia infection in the development of coronary atherosclerosis that should be further studied.

Early and late outcome following deployment of a new flexible tantalum intracoronary stent in dogs

A new radiopaque, highly flexible balloon-expandable tantalum stent was tested. Thirty-six of 40 stents were successfully deployed percutaneously in the coronary arteries of 31 dogs. The dogs were given aspirin before, intravenous heparin during, and aspirin alone after the procedure. One dog died at 24 hours because of coronary occlusion following traumatic implantation. Four dogs were put to death early, revealing re-endothelialization by 9 days. Eleven dogs were put to death from 2 weeks to 9 months during long-term follow-up, showing all vessels widely patent with the stent uniformly embedded within a stable neointimal layer. Follow-up arteriography showed patency in all remaining stents up to 1 year, with no perforation or aneurysm formation. Four stents were placed into canine peripheral arteries and were removed percutaneously after deployment. Pathology revealed no significant trauma to involved vessels. This tantalum stent exhibits feasibility of percutaneous deployment, early neointimal formation, low thrombogenicity on long-term aspirin therapy alone, and patency up to 1 year in this canine model.

Prospective analysis of possible myocardial damage or hemolysis occurring as a result of prolonged autoperfusion angioplasty in humans

OBJECTIVES

The purpose of this study was to further explore the procedural safety of prolonged (15-min) dilation using an autoperfusion coronary angioplasty balloon by assessing the degree of myocardial damage or hemolysis, if any, occurring as a result of the procedure.

BACKGROUND

Prolonged balloon inflation periods may be beneficial during percutaneous transluminal coronary angioplasty. The duration of standard balloon angioplasty is often limited by the occurrence of myocardial ischemia due to loss of anterograde blood flow. Autoperfusion angioplasty allows continued myocardial perfusion during balloon inflation and has previously been shown to reduce but not totally eliminate acute myocardial ischemia during prolonged (up to 15 min) balloon inflation. The risk of intravascular hemolysis as a result of autoperfusion angioplasty has not yet been fully delineated.

METHODS

Sixty-two consecutive patients (76% men; mean age 58 years) undergoing elective percutaneous transluminal coronary angioplasty of a single lesion were studied. Serial electrocardiographic and creatine kinase MB isoenzyme data were examined to detect evidence of myocardial damage. Tests for hemolysis (plasma free hemoglobin, serum haptoglobin and serum lactate dehydrogenase) were obtained in the 1st 24 consecutive patients.

RESULTS

Inflation time was 14 +/- 4 min (mean +/- SD) and the procedure was successful (less than or equal to 50% residual lesion stenosis) in 59 patients (95%). Electrocardiographic evidence of myocardial infarction (greater than 1 mm persistent ST segment depression, greater than 1 mm ST segment elevation or new Q waves) was not observed in any patient. Cardiac enzyme assays were within the normal range in all patients. No evidence of hemolysis was found in the 24 consecutive patients studied.

CONCLUSIONS

We conclude that prolonged autoperfusion angioplasty can be performed in patients without clinical evidence of myocardial damage or hemolysis.

Direct in vivo gene transfer into the coronary and peripheral vasculatures of the intact dog

Gene therapy approaches have been suggested for the treatment of cardiovascular disease. Recently, direct transfer of the gene encoding beta-galactosidase into peripheral arteries of the pig has been demonstrated. To determine whether this approach is applicable to other arterial beds and to other species, we first evaluated the use of beta-galactosidase as a marker protein in the canine model. We demonstrate that variable but substantial endogenous beta-galactosidase-like activity is induced by manipulation of canine peripheral arteries, which precludes the use of this marker protein in evaluating the efficiency of gene transfer in this model. A marker gene encoding firefly luciferase was then evaluated, and background luciferase activity was found to be low in the dog even after arterial manipulation. Using the luciferase gene, we then demonstrated lipid-mediated gene transfer directly into both coronary and peripheral arteries of the intact dog. These results indicate the feasibility of in vivo gene transfer into coronary arteries and demonstrate the use of the luciferase marker protein in quantifying recombinant protein expression following gene transfer in canine models. This simple and effective method for direct in vivo gene transfer into coronary and peripheral arteries may be applicable to the localized production of therapeutically important proteins for the treatment of cardiovascular diseases.