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Eur J Cardiothorac Surg 2003;23:179-186
© 2003 Elsevier Science NL
The University of Sydney, Cardiothoracic Surgical Unit, Royal Prince Alfred Hospital, The Baird Institute for Heart and Lung Surgical Research, Sydney, NSW, Australia
Received 20 August 2002; received in revised form 13 November 2002; accepted 17 November 2002.
* Corresponding author. The Cardiothoracic Surgical Unit, Level 8, Page Chest Pavilion, Royal Prince Alfred Hospital, Missenden Road, Camperdown, NSW 2050, Australia. Tel.: +61-2-9515-8629; fax: +61-2-9515-6378
e-mail: cfh{at}cts.rpa.cs.nsw.gov.au
| Abstract |
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Key Words: Interval Coronary artery bypass grafting Percutaneous transluminal coronary angioplasty
| 1. Introduction |
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The aim of this study was to analyze those patients who underwent initially successful PTCA and developed recurrent symptoms, and then ultimately required a CABG procedure. Outcomes were studied for these patients and were compared to those patients that were treated by primary elective CABG over the same time period at RPAH. The costs of interventional cardiology procedures and definitive surgery were calculated for the interval study group.
| 2. Patients and methods |
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A successful PTCA was defined as dilatation of a targeted coronary stenosis (or stenoses) such that the residual luminal narrowing was less than 40%, and not associated with complications. Patients requiring emergency CABG (within 24 h) following initial PTCA (74 patients), or those who had unsuccessful angioplasty were excluded from the interval group and have been reported elsewhere.
The hospital's prospectively maintained coronary artery surgery register and cardiology clinical reporting systems were analyzed and a comprehensive retrospective review was undertaken of all consecutive patient records spanning the study period. Patient baseline characteristics analyzed included patient age, gender, features of clinical presentation, New York Heart Association (NYHA) class symptoms, time duration of angina, and left ventricular ejection fraction. Risk factors for ischemic heart disease, including diabetes mellitus, smoking history, hypertension, hyperlipidemia, obesity, and family history of coronary disease were also compared. Pre-operative co-morbidities included valvular heart disease, peripheral ischemic vascular disease, cerebrovascular disease, renal failure, and chronic airways limitation. The times of all procedures were recorded. The time interval between initial PTCA to CABG was determined for the interval study group. In both groups the duration of cardiopulmonary bypass, and the number of distal anastomoses were compared.
Post-operative complications assessed included new-onset Q wave acute myocardial infarction (AMI), significant arrhythmia, low cardiac output syndrome (defined as cardiac index <1.5 l/min per m2), respiratory failure (requiring ventilatory support for greater than 24 h), and requirement for renal dialysis. Other factors measured included catecholamine requirement, postoperative haemorrhage of greater than 1.5 l, re-operation for haemorrhage, late pericardial tamponade, adverse neurological events, significant wound infection, and systemic or pulmonary thromboembolism.
Thirty-day mortality, and primary cause of death were determined for all patients. Causative factors for death included low cardiac output, AMI, cardiac dysrhythmia, respiratory failure, renal failure, haemorrhage, and pulmonary embolus. Initial outcome after CABG, and length of hospital stay were also recorded.
2.1. Statistics
Comparison between the Interval and Control Groups was performed using the SPSS statistical software package. Odds ratios with 95% confidence intervals and
2 analysis were used for count data, and two-tailed Student's t-tests were used for continuous data as appropriate.
2.2. Data for hospital charges
Hospital costs, in monetary terms, were calculated from Diagnosis Related Group (DRG) allocated data. This data, collected prospectively is used by the relevant health departments to determine the relative costs for all surgical procedures grouped by type. For procedures that have high volume and relatively standard components, these cost calculations closely reflected the actual cost for treatment options (i.e. PTCA, CABG). DRG cost data, although averaged are based on actual costs of individual patient episodes of care and include the costs of resources consumed and the appropriate share of the overheads [9]. Evaluation of the RPAH DRG data showed that information for the financial year 19951996 was the most refined for the four groups we sought to compare, namely coronary angiography, PTCA and CABG (with and without complications). Therefore the 19951996 RPAH DRG cost for these procedures were used for subsequent calculations (see Fig. 4).
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| 3. Results |
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3.2. Patient characteristics at baseline (before CABG)
Patient characteristics before CABG are outlined in Table 1. There were no significant differences between the interval and control groups for the incidence of major medical comorbidities or coronary artery disease risk factors. The control population had a slightly greater proportion of male patients than the interval group (80 versus 75%, P<0.05) and had a lower mean pre-operative left ventricular ejection fraction (0.56 versus 0.65, P<0.05). A comparison of pre-operative New York Heart Association class symptoms for the study groups is shown in Fig. 1
. A significantly higher number of patients in the interval population presented for CABG with unstable angina pectoris (70 versus 52%, P<0.05). A greater proportion of patients in the control group were classified as being obese (47 versus 33%, P<0.05), and had a history of smoking (67 versus 60%, P<0.05) compared with the interval population.
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| 4. Comment |
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There is a growing tendency for CABG to be reserved for those patients in whom PTCA has failed either in the emergent or long-term setting, or for those in whom PTCA was clearly contraindicated [10,11]. The patients in the interval group in our study who underwent CABG following PTCA, tended to have less severe intrinsic coronary disease than the controls (see Table 2). These patients were more likely to present clinically with unstable angina pectoris, this being the major mode of presentation in 70% of interval patients, in comparison to 52% of controls (P<0.05). Furthermore, a greater number of patients in the interval group had NYHA class 4 symptoms, despite having undergone previous PTCA (see Fig. 1).
In this study, patients who had previously undergone a CABG procedure prior to PTCA were excluded from the interval group, while patients having a redo-CABG, or a second surgical bypass operation, were excluded from the control group. This was appropriate because recurrent stenosis of a coronary graft may be the result of a different disease process as compared to the atherosclerosis that occurs in a native coronary artery. In addition, it was not possible to accurately determine the pathological process responsible for recurrent disease in the different types of conduit vessels used for the various coronary grafts.
The interval population had a significantly lower mean number of diseased coronary vessels than did the controls (2.0 versus 2.6, P<0.05). This population also had a significantly lower incidence of triple-vessel atherosclerotic disease, and a substantially less frequent stenosis of the left main coronary artery (1.3 versus 3.4%, P<0.05). As would thus be expected, the interval population required a lower average number of coronary anastomoses at the time of operation than did the controls (2.9 versus 4.1, P<0.05). This data suggests that the patient population currently being offered primary CABG, as opposed to PTCA as primary treatment for coronary disease, is skewed towards a higher baseline risk for adverse outcomes, given their higher inherent rate of more advanced pathology at baseline. This finding parallels previous reports [8,12].
Despite this shift in patient demographics, however, numerous studies have reported similar prognostic outcomes in patients randomized to either PTCA or CABG for their initial myocardial revascularization procedure [17]. At follow-up of 13 years, there are no reported significant differences between patients who underwent PTCA or CABG with respect to overall mortality or with regard to the composite endpoint of cardiac death plus non-fatal AMI [13,14]. This is with the notable exception of improved 5-year survival amongst patients with diabetes treated by CABG rather than PTCA [1]. Similarly, our data demonstrated that the incidence of major perioperative complications did not significantly differ between interval and control groups, and the overall 30-day mortality was comparable between both patient populations (see Table 4). This supports the assertion that, although the primary CABG population may have greater pre-intervention severity of coronary disease, they are not subject to increased adverse outcomes in comparison to those patients treated by PTCA before definitive surgical management.
Previous studies analyzing cumulative data of the trials comparing patients randomized to either PTCA or CABG report significantly higher reintervention rates for those patients receiving an initial PTCA in comparison to those patients treated by primary CABG [13,14]. Overall reintervention rates of greater than 30% have been reported for those patients receiving an initial PTCA, in comparison to a 1-year additional procedure rate of just over 3% for patients treated by primary CABG [13]. The Bypass Angioplasty Revascularization Investigation (BARI) [1] described an even more impressive difference in reintervention rates between these two patient populations. BARI reported a 5-year reintervention rate of 8% for the CABG group, in comparison to 54% for the PTCA population. Moreover, in this trial, 19% of patients assigned to PTCA required more than one additional revascularization procedure, in comparison to only 3% of patients initially treated by CABG, and 31% of PTCA-treated patients ultimately required CABG. Further research needs to be performed to determine the rate of myocardial infarction as a result of repeated percutaneous coronary interventions in those patients who require CABG following initially successful PTCA.
PTCA may be initially advocated in the hope that the need for CABG may be avoided completely, or at least delayed by a significant period of time. The 361 patients in our cohort who initially received a PTCA procedure were all classified as having had a successful outcome, as the residual luminal narrowing of the vessel post-dilatation was less than 40%. Despite this perceived success these procedures only served to delay coronary graft surgery by a mean of 13.7 months, and median time of 4 months (see Fig. 2a). Johnson et al. [8] reported a mean time interval of 16.7 months between initially successful PTCA and CABG. The data in the present study suggested an even shorter duration of benefit conferred by angioplasty in those patients who required CABG following initially successful PTCA.
The cost of a single PTCA procedure (AUD$3824) is substantially lower than that of CABG (AUD$11 403 without complication, AUD$18 210 with complication), a finding that has been consistently reported [15,16]. However, this seemingly impressive cost differential between PTCA and CABG patient populations substantially narrows over the ensuing follow-up period, as the additional, often multiple percutaneous interventions required in the interval group become incorporated into the financial analysis [17]. Stents may reduce the restenosis rate and decrease the number needing surgery. However, a recent study by Heuser et al. [18] reported patients who underwent balloon angioplasty when compared to those who received coronary stenting had no statistically significant differences in regard to requirement for additional percutaneous coronary intervention or coronary artery bypass during a 6-month follow-up period. This study reported direct cardiac catheterization laboratory costs associated with coronary stenting were nearly 2.5 times greater than standard balloon angioplasty, and that the cost-effectiveness of coronary stenting, needs to be established [18].
Hospital readmission costs were not available and could not be considered in the analysis, and this is a limitation of our study. The cost to achieve coronary revascularization for a patient in the interval group on average substantially exceeded the cost of a coronary bypass operation alone (Fig. 4). These data indicate that a single CABG procedure is a more financially cost-effective option for appropriately selected patients by avoiding repeated interventional procedures. The reported literature suggests that CABG is a definitively more cost-effective treatment option for patients with triple-vessel disease, as well as for diabetic patients, particularly in light of the significant survival advantage conferred by surgery to this latter patient cohort [15,16].
When comparing the cost of PTCA with CABG, it is also important to consider the non-fiscal aspects of the burden of treatment. Whereas there was less initial post-treatment morbidity after a PTCA procedure than after coronary surgery, this perceived advantage of PTCA steadily became eroded over time. Patients who underwent primary PTCA tended to require repeated hospital admissions for multiple additional angiograms and reinterventions. Moreover, trials comparing outcomes after either PTCA or CABG, while describing similar overall rates of mortality for the two procedures, consistently reported that patients treated by CABG were more likely to be free of angina at follow-up [13,14]. It is thus not surprising that functional status and quality of life after coronary surgery have been reported as exceeding that after PTCA in the first 3 years of follow-up [15]. There has also been the suggestion of a trend towards a more favorable outcome in terms of subjective perceived patient energy levels after CABG than after angioplasty [19]. Based on this published literature and the findings in our own study we believe that the quality of life advantage conferred by CABG is even more significant when one considers that the mean time interval between initial PTCA and subsequent CABG in our interval patient cohort was only approximately 1 year (see Fig. 2a). Interestingly, the time interval based on the year the primary PTCA was performed, has decreased over the study period. This is possibly due to intervention on more complicated and higher risk patients (see Fig. 2b).
There is little doubt that PTCA remains a successful revascularization procedure for the patient with coronary disease not responsive to medical therapy [13,14]. However, coronary bypass surgery provides durable long-term control of ischemic symptoms with very low requirement for repeat intervention even at 5-year follow up [1]. The primary method of myocardial revascularization needs to be carefully selected to obtain durable symptom control for patients with coronary artery disease. PTCA procedures often need to be repeated over time [1,13,14] and may serve only to delay coronary surgery, at substantial financial and personal cost.
| Acknowledgments |
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| References |
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