Coronary artery stenting: indications and cost implications

Measurement of in vitro and in vivo stent geometry and deformation by means of 3D imaging and stereo-photogrammetry

PURPOSE

To quantify variability of in vitro and in vivo measurement of 3D device geometry using 3D and biplanar imaging.

METHODS

Comparison of stent reconstruction is reported for in vitro coronary stent deployment (using micro-CT and optical stereo-photogrammetry) and in vivo pulmonary valve stent deformation (using 4DCT and biplanar fluoroscopy). Coronary stent strut length and inter-strut angle were compared in the fully deployed configuration. Local (inter-strut angle) and global (dog-boning ratio) measures of stent deformation were reported during stent deployment. Pulmonary valve stent geometry was assessed throughout the cardiac cycle by reconstruction of stent geometry and measurement of stent diameter.

RESULTS

Good agreement was obtained between methods for assessment of coronary stent geometry with maximum disagreement of +/- 0.03 mm (length) and +/- 3 degrees (angle). The stent underwent large, non-uniform, local deformations during balloon inflation, which did not always correlate with changes in stent diameter. Three-dimensional reconstruction of the pulmonary valve stent was feasible for all frames of the fluoroscopy and for 4DCT images, with good correlation between the diameters calculated from the two methods. The largest compression of the stent during the cardiac cycle was 6.98% measured from fluoroscopy and 7.92% from 4DCT, both in the most distal ring.

CONCLUSIONS

Quantitative assessment of stent geometry reconstructed from biplanar imaging methods in vitro and in vivo has shown good agreement with geometry reconstructed from 3D techniques. As a result of their short image acquisition time, biplanar methods may have significant advantages in the measurement of dynamic 3D stent deformation.

Resource utilization, cost, and health status impacts of coronary stent versus "optimal" percutaneous coronary angioplasty: results from the OPUS-I trial

In the OPUS-I trial, primary coronary stent implantation reduced 6-month composite incidence of death, myocardial infarction, cardiac surgery, or target vessel revascularization relative to a strategy of initial PTCA with provisional stenting in patients undergoing single vessel coronary angioplasty. The purpose of this research was to compare the economic and health status impacts of each treatment strategy. Resource utilization data were collected for the 479 patients randomized in OPUS-I. Itemized cost estimates were derived from primary hospital charge data gathered in previous multicenter trials evaluating coronary stents, and adjusted to approximate 1997 Medicare-based costs for a cardiac population. Health status at 6 months was assessed using the Seattle Angina Questionnaire (SAQ). Initial procedure related costs for patients treated with a primary stent strategy were higher than those treated with optimal PTCA/provisional stent ($5,389 vs $4,339, P < 0.001). Costs of initial hospitalization were also higher for patients in the primary stent group ($9,234 vs $8,434, P < 0.01) chiefly because of the cost differences in the index revascularization. Mean 6-month costs were similar in the two groups; however, there was a slight cost advantage associated with primary stenting. Bootstrap replication of 6-month cost data sustained the economic attractiveness of the primary stent strategy. There were no differences in SAQ scores between treatment groups. In patients undergoing single vessel coronary angioplasty, routine stent implantation improves important clinical outcomes at comparable, or even reduced cost, compared to a strategy of initial balloon angioplasty with provisional stenting.

Long-term survival in 11,661 patients with multivessel coronary artery disease in the era of stenting: a report from the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) Investigators

BACKGROUND

Studies of survival of patients with multivessel coronary artery disease (MVD) in the prestent era suggested that outcomes after coronary artery bypass surgery (CABG) are similar to those after percutaneous coronary intervention (PCI) in subsets of coronary severity. The purpose of this study of the Alberta Provincial Project for Outcome Assessment in Coronary Heart Disease (APPROACH) was to examine the association between treatment and survival up to 5 years in patients with MVD enrolled from 1995 through 1998.

METHODS AND RESULTS

Data on patient characteristics were obtained at the time of the initial coronary angiography. Survival was determined through data linkage to the provincial Bureau of Vital Statistics. Risk-adjusted hazard ratios were calculated to compare different treatments. In the 11,661 patients with MVD, CABG was the initial therapy in 3782, PCI in 3540, and medical therapy in 4339. Cumulative 5-year survival was 91.4% with CABG, 91.9% with PCI, and 82.9% with medical therapy (P <.001). Hazard ratios were CABG: medical 0.53 (95% confidence interval [CI] 0.46-0.71), PCI: medical 0.65 (95% CI 0.56-0.74), and CABG: PCI 0.81 (95% CI 0.68-0.96). Analysis across coronary severity groups revealed a benefit of CABG compared with PCI only in the group with severe left main CAD: 0.30 (95% CI 0.17-0.54).

CONCLUSIONS

In a multicenter clinical setting, MVD patients treated with revascularization have significantly higher 5-year survival rate than do those treated medically. Risk-adjusted comparison reveals PCI treatment to be associated with long-term survival similar to treatment with CABG in all coronary severity subgroups except the group with severe left main coronary artery disease. Patient selection factors are likely to be contributing to these findings.

MR imaging in the presence of vascular stents: A systematic assessment of artifacts for various stent orientations, sequence types, and field strengths

A systematic evaluation of the potential quality of magnetic resonance images recorded in the presence of metallic stents was performed on a low-field open imager operating at 0.2 T and on a high-field closed unit operating at 1.0 T. Eight different stent types were examined by two-dimensional gradient-echo sequences with echo times of 4 and 10 msec and by a fast spin-echo technique. In addition, a three-dimensional gradient-echo sequence was applied with an echo time of 2.4 msec. A set of sequence and slice parameters was used on both scanners. Thus, artifacts due to susceptibility effects depending on the magnetic field strength could be distinguished from radiofrequency shielding effects in the lumen of the stents (independent of the field strength). Nine different orthogonal orientations of the stent axis and the image (in terms of slice, read, and phase-encoding direction) were tested, and the artifacts (extension of signal void and visibility of the lumen) were compared. The optimal strategy for visualization of vascular and perivascular regions outside the stents was fast spin-echo imaging with the stent axis and read direction parallel to the static field. Susceptibility-induced signal void in gradient-echo images was minimal using the three-dimensional approach. Increased transmitter amplitudes above usual values provided clearly improved insight in the lumen using gradient-echo sequences.

Stent implantation without predilation in patients with a single, noncalcified coronary artery lesion

The purpose of this study was to assess the feasibility of stent implantation without predilation in patients with a single, noncalcified coronary artery lesion. A total of 122 patients were randomized to receive a stent with or without predilation; direct stent placement was possible in 59 of the 61 patients (97%) with an immediate and long-term clinical follow-up similar to that observed in the group of patients treated conventionally.

Trends in clinical and economic outcomes of coronary angioplasty from 1992 to 1995: a population-based analysis

BACKGROUND

The impact of recent developments in coronary angioplasty on the broad spectrum of patients treated in routine practice is largely undefined. Analysis of population-based data can provide insight into trends in clinical outcomes and associated costs of coronary angioplasty procedures.

METHODS AND RESULTS

With the use of a comprehensive hospital discharge database covering more than 11 million Canadians, we analyzed 12,748 first-time angioplasty procedures performed from 1992 to 1995 inclusive. Patient demographics and major adverse events were recorded. With the use of forward linkage, readmissions within 12 months were classified according to procedure performed and/or most responsible diagnosis. The proportion of patients readmitted, the number of readmissions per index procedure, and diagnosis-specific readmission costs were compared by calendar year. Over the 4-year study period, there was a 21% increase in the annual volume of index procedures. There were no statistically significant differences between 1992 and 1995 in sex distribution, mean age, comorbid conditions, length of stay, or need for coronary bypass surgery related to the index procedure. The all-cause readmission rate declined from 51.6% to 47.2% between 1992 and 1995 (P <.001), primarily because of a decline in the admission rate for repeat revascularization from 24.8% to 19.6% (P <.001). The 12-month readmission cost declined by $435 (1994 Canadian dollars) per patient.

CONCLUSIONS

The clinical outcomes of coronary angioplasty in a broad cohort of patients have improved in recent years. Although readmissions within 1 year of an angioplasty procedure remain common, the number related to repeat revascularization has declined, with an associated decline in downstream costs.

Pathophysiology and treatment of single-vessel coronary artery disease

The optimal treatment of patients with single-vessel coronary artery disease (CAD) and chronic stable angina is controversial. Therapeutic options include medical therapy with pharmacologic agents and/or coronary revascularization via surgery (coronary artery bypass grafting [CABG]), percutaneous transluminal coronary angioplasty (PTCA), and/or other transcatheter techniques. Early studies found no difference in survival between medical and surgical treatment of patients with single-vessel disease and chronic stable angina. Although PTCA has been shown to improve symptoms and quality of life in patients with single-vessel disease and severe symptoms, improvement in survival and prevention of future events are not established and multiple PTCA procedures or subsequent surgical treatment may be necessary. Medical therapy may be preferred in patients with mild or no symptoms. In patients with chronic stable angina, PTCA practice may not be consistent with current guidelines, particularly obtaining laboratory evidence of ischemia before the procedure. Stenoses that may lead to future coronary events cannot be accurately identified by angiography without evidence of ischemia or symptoms. Currently available comparative studies of patients with CAD do not reflect the impact of stent procedures and aggressive lipid lowering. Therefore, diagnostic and treatment options should be individualized in patients with single-vessel disease and chronic stable angina, and additional randomized trials are necessary to determine the optimal management of these patients.