Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence

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JJCC-1443; No. of Pages 9 Journal of Cardiology xxx (2017) xxx–xxx

Contents lists available at ScienceDirect

Journal of Cardiology journal homepage: www.elsevier.com/locate/jjcc

Review

Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence Pasi P. Karjalainen (PhD)*, Wail Nammas (PhD) Heart Center, Satakunta Central Hospital, Pori, Finland

A R T I C L E I N F O

A B S T R A C T

Article history: Received 2 November 2016 Received in revised form 29 November 2016 Accepted 8 December 2016 Available online xxx

Chronic total occlusion (CTO) is a challenging subset of coronary artery disease that is commonly encountered in real-world practice; it is associated with worse long-term prognosis. Observational studies suggest that percutaneous coronary intervention (PCI) for CTO is associated with reduction in myocardial ischemia and improvement in quality of life and left ventricular function. Some observational studies suggested that CTO-PCI is associated with improvement of the ‘hard’ clinical endpoints; others did not. Nearly all these studies compared the clinical outcome of successful versus failed PCI, rather than comparing the outcome of a whole CTO-PCI cohort versus a ‘true’ control group. Interestingly, in observational studies that compared the outcome of CTO-PCI versus optimal medical treatment, long-term mortality was comparable between the two strategies. In patients with multivessel disease and CTO, complete revascularization is more often achieved by coronary artery bypass grafting than by PCI; the SYNTAX score of these patients often favors surgical revascularization according to the current guidelines. The current guidelines reflect the divergence of opinion on the usefulness/ benefit of CTO-PCI, mainly due to the lack of randomized trials. Evidence is awaited from three ongoing randomized controlled trials comparing PCI versus optimal medical treatment in the setting of CTO. ß 2016 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Keywords: Chronic total occlusion Percutaneous coronary intervention Outcome

Contents Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Collaterals to CTO . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . What do the proponents of percutaneous revascularization say? . Improvement of quality of life . . . . . . . . . . . . . . . . . . . . . . . Improvement in the surrogate endpoints . . . . . . . . . . . . . . Impact on the cardiovascular outcome . . . . . . . . . . . . . . . . Studies comparing CTO-PCI versus medical treatment . . . . Meta-analyses of the long-term cardiovascular outcome . . Reappraisal of the quality of evidence . . . . . . . . . . . . . . . . . . . . . . Funding sources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conflict of interest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . References . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Introduction Defined as 100% coronary occlusion with Thrombolysis in Myocardial Infarction grade 0 distal flow persistent for >3 months,

* Corresponding author at: Heart Center, Satakunta Central Hospital, Sairaalantie 3, FIN-28500 Pori, Finland. Fax: +358 2 6277757. E-mail address: pasi.karjalainen@satshp.fi (P.P. Karjalainen).

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chronic total occlusion (CTO) is commonly encountered in clinical practice. In North American reports, the prevalence of CTO ranged from 18.4% in patients with significant coronary artery disease who underwent elective coronary angiography, to 31% in all patients who underwent coronary angiography not including coronary artery bypass grafting (CABG); the prevalence ranged from 16% to 19% in the CERDO-Kyoto Registry cohort-2 from Japan [1–3]. In the European STAR Registry the prevalence was 33% in stable patients undergoing first diagnostic angiography; in this registry, CTO was

http://dx.doi.org/10.1016/j.jjcc.2016.12.006 0914-5087/ß 2016 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.

Please cite this article in press as: Karjalainen PP, Nammas W. Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence. J Cardiol (2017), http://dx.doi.org/10.1016/j.jjcc.2016.12.006

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JJCC-1443; No. of Pages 9 P.P. Karjalainen, W. Nammas / Journal of Cardiology xxx (2017) xxx–xxx

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associated with higher 1-year mortality (attributed to confounders, such as diabetes and left ventricular dysfunction) [4]. Comparably, in the Italian Registry of Chronic Total Occlusion (IRCTO), the prevalence of patients with 1 CTO was 12.3% [5]. Patients with 1 CTO have worse prognosis, even after revascularization of another vessel territory. CTO of a non-infarct-related artery independently predicted long-term mortality in patients who underwent primary percutaneous coronary intervention (PCI) for ST-elevation myocardial infarction (MI) [6,7]. In patients with 3vessel disease who presented with non-ST-elevation MI, CTO of a non-infarct-related artery was independently associated with 12month mortality [8]. Collaterals to CTO Long-standing CTO is usually accompanied by the development of collaterals. Viability in the CTO territory is not a prerequisite for collateral formation: in 47 patients with CTO, collaterals predicted viability with modest sensitivity and specificity (75% and 65.7%) [9]. Although, theoretically, collaterals prevent myocardial necrosis and secure metabolic needs for resting contractile function in the CTO territory, evidence suggests that collaterals are insufficient to prevent baseline ischemia or to provide adequate flow during increased needs. In 50 symptomatic patients who underwent CTOPCI, resting ischemia was present (fractional flow reserve <0.08) in 78% of the patients, even with well-developed collaterals [10]. Increased collateral flow under pharmacological stress was observed in only 7% of patients with CTO without prior MI (n = 62); coronary steal occurred in 36%; neither collateral flow reserve nor coronary steal was related to the extent of regional contractility [11]. Furthermore, in 21 patients with non-revascularized CTO, collaterals (61%) failed to predict cardiac events (23 months follow-up) or

freedom from ischemia on myocardial perfusion imaging (MPI); ischemia on MPI predicted events in these patients [12]. In view of the small sample size and the limitation of retrospective design, the latter results should be taken with caution. What do the proponents of percutaneous revascularization say? Traditionally, CTO represents a challenging subset for the interventional cardiologist; CTO-PCI has been associated with low success rates and high complication rates [13–16]. Yet, important developments in the field including dedicated equipment and sophisticated techniques have triggered growing interest in CTOPCI [17]. In observational studies, successful CTO-PCI was associated with improvement in quality of life, surrogate endpoints, and cardiovascular outcome. Improvement of quality of life In observational studies, successful, versus failed, CTO-PCI was associated with greater improvement in quality of life parameters, at short- and long-term follow-up (Table 1) [18–20]. Improvement in quality of life parameters was reported after CTO revascularization (PCI or CABG) at 1 year, compared with baseline; no such improvement occurred with medical treatment [21]. Moreover, improvement in quality of life was comparable between CTO-PCI and non-CTO-PCI [22]. Improvement in the surrogate endpoints Observational studies demonstrated improvement in global and regional left ventricular function in patients who underwent

Table 1 Studies of quality of life following CTO-PCI. Study

Ref.

Center

Borgia et al.

[18]

Single-center

302

78%

Successful versus failed CTO-PCI

SAQ-UK

4 years

Yes

Grantham et al.

[19]

Multi-center

125

55%

Successful versus failed CTO-PCI

SAQ

1 month

Yes

Ciec´wierz et al.

[20]

Single-center

276 (1:1 matched pairs)

Successful versus failed CTO-PCI

Angina symptoms

6 months and 2 years

Yes

Wijeysundera et al.

[21]

Multi-center

387 (only 46 underwent PCI)

78.8%

Treatment groups (PCI, CABG, MT) were compared with baseline

SAQ

1 year

Safley et al.

[22]

Multi-center

147

85% (CTO-PCI) 98% (non-CTO-PCI)

CTO-PCI versus non-CTO-PCI

SAQ

6 months

No. of patients

Success rate

Comparison groups

Evaluation

Follow-up duration

Adjustment

Yes

Results Improvement of physical limitation, angina frequency, and treatment satisfaction in successful versus failed CTO-PCI Improvement of physical limitation, angina frequency, and QOL in successful versus failed CTO-PCI, more in symptomatic patients Greater improvement of angina burden, and more resolution of angina in successful versus failed CTO-PCI, both at 6 months and 2 years Improvement of physical limitation, angina frequency, angina stability, disease perception, treatment satisfaction, and EQ5D in patients who underwent revascularization by PCI and CABG at follow-up, compared with baseline; no improvement in MT group Comparable improvement of physical limitation, angina frequency, EQ5D, QOL, and Rose Dyspnea Score in successful CTO-PCI and successful non-CTO-PCI

CABG, coronary artery bypass grafting; CTO, chronic total occlusion; EQ5D, European quality of life-5 dimensions; MT, medical treatment; PCI, percutaneous coronary intervention; QOL, quality of life; SAQ, Seattle Angina Questionnaire.

Please cite this article in press as: Karjalainen PP, Nammas W. Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence. J Cardiol (2017), http://dx.doi.org/10.1016/j.jjcc.2016.12.006

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JJCC-1443; No. of Pages 9 P.P. Karjalainen, W. Nammas / Journal of Cardiology xxx (2017) xxx–xxx

successful CTO-PCI, at short- mid-, and long-term follow-up, compared with baseline (Table 2) [23–27]. Similarly, successful CTO-PCI was associated with improvement in myocardial ischemia at mid-term follow-up, compared with baseline [27–29]. Indices of electrical vulnerability also improved 48 h following successful CTO-PCI [30]. In a weighted meta-analysis, left ventricular ejection fraction improved after successful CTO-PCI, versus baseline, with a pooled estimate of 4.44% (95% confidence interval 3.52–5.35, p < 0.01), after a wide range of follow-up durations. An important limitation was moderate heterogeneity (I2 = 44%) among included studies [31]. Impact on the cardiovascular outcome Studies that demonstrated better cardiovascular outcome with successful, versus failed, CTO-PCI are summarized in Table 3. Registry data demonstrated that successful, versus failed, CTO-PCI was associated with reduction in mortality and other major adverse cardiac events (MACE), at long-term follow-up [13,16,32–35].

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Consistent results were obtained with the retrograde approach [36]. Yet, in a single-center study, survival benefit seen with successful, versus failed, CTO-PCI was restricted to patients with multi-vessel disease (MVD) [37]. In other studies, survival benefit varied with the target epicardial vessel [14,38]. In the Italian Registry of Chronic Total Occlusion, CTO-PCI was associated with lower cardiac mortality, compared with medical treatment and CABG (1.4% versus 4.7% and 6.3%; p < 0.001 and p < 0.001, respectively); the benefit persisted after propensity score matched analysis [5]. On the other hand, studies that demonstrated comparable cardiovascular outcome with successful, versus failed, CTO-PCI are summarized in Table 4. All showed comparable mortality and other MACE between the two comparison groups, at long-term follow-up, either in adjusted, or in both adjusted and unadjusted analysis [3,18,20,39–43]. However, as an inherent limitation to all registries and observational studies, the retrospective analysis of data could have introduced selection bias, added to the absence of information on the exact medical treatment received in the comparison groups.

Table 2 Studies of surrogate endpoints following CTO-PCI. Study

Ref.

Center

Chung et al.

[23]

Single-center

Erdogan et al.

[24]

Baks et al.

No. of patients

Comparison groups

Evaluation

Follow-up duration

75

Successful CTO-PCI at follow-up versus baseline

Left ventriculography

6 months

Single-center

129

Successful CTO-PCI at follow-up versus baseline

Echocardiography

1 month

[25]

Single-center

27

Successful CTO-PCI at follow-up versus baseline

Cardiac magnetic resonance imaging

5 months

Kirschbaum et al.

[26]

Single-center

21

Successful CTO-PCI at follow-up versus baseline

Cardiac magnetic resonance imaging

3 years

Cheng et al.

[27]

Single-center

17

Successful CTO-PCI at follow-up versus baseline

Cardiac magnetic resonance imaging

24 h and 6 months

Safley et al.

[28]

Single-center

301

Successful CTO-PCI at follow-up versus baseline

Myocardial perfusion imaging

Within 12 months after CTO-PCI

Pujadas et al.

[29]

43

Successful CTO-PCI at follow-up versus baseline and versus failed CTO-PCI

Cardiac magnetic resonance imaging

6 months

Cetin et al.

[30]

Single-center

90

Successful CTO-PCI at follow-up versus baseline

Electrocardiography

48 h

Hoebers et al.

[31]

Meta-analysis

34 studies, 2243 patients

Successful CTO-PCI at follow-up versus baseline

Left ventricular ejection fraction

range 1–36 months

Results Global and regional left ventricular function improved in successful CTO-PCI patients versus baseline in those without prior myocardial infarction. Left ventricular dimensions, ejection fraction, and global longitudinal strain improved in successful CTO-PCI patients versus baseline. Ventricular dimensions improved versus baseline; ejection fraction did not; segmental wall thickening improved in segments with a transmural extent of infarction less than 25%. Ventricular dimensions improved versus baseline; ejection fraction did not; segmental wall thickening improved in segments without transmural scar. Transmural extent of infarction predicted segmental function improvement. Both hyperemic myocardial blood flow and contractility of treated segments improved at 24 h, and at 6 months, versus baseline. Ischemic burden improved versus baseline, baseline ischemic burden 12.5% was the optimal cutoff value that predicts improvement at follow-up. Inducible perfusion defects decreased in patients who underwent successful CTO-PCI at 6 months, versus baseline; regional contractile function and NYHA class improved after successful versus failed CTO-PCI at 6 months. Electrical vulnerability parameters improved versus baseline. Left ventricular ejection fraction improved versus baseline; no improvement occurred after failed CTO-PCI.

CTO, chronic total occlusion; NYHA, New York Heart Association; PCI, percutaneous coronary intervention.

Please cite this article in press as: Karjalainen PP, Nammas W. Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence. J Cardiol (2017), http://dx.doi.org/10.1016/j.jjcc.2016.12.006

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Table 3 Studies that demonstrated better cardiovascular outcome with successful versus failed CTO-PCI. Study

Ref.

Center

No. of patients

Success rate

Comparison groups

Endpoint

Follow-up duration

George et al.

[13]

Multi-center registry

13,443

70.6%

Successful versus failed CTO-PCI

Survival

Median 2.65 years

Mehran et al.

[16]

Multi-center registry

1791

68%

Successful versus failed CTO-PCI

Cardiac mortality, need for CABG

5 years

Claessen et al.

[32]

Multi-center registry

395 diabetic patients

69.6%

Successful versus failed CTO-PCI

Mortality, need for CABG

3 years

Chen et al.

[33]

Multi-center registry

86.8% 152 patients (CTO-PCI in hospitals without surgical backup)

Successful versus failed CTO-PCI

MACE

1 and 3 years

Niccoli et al.

[34]

Single-center study

317

62%

Successful versus failed CTO-PCI

MACE

Mean 3 years

Jones et al.

[35]

Single-center registry

836

69.6%

Successful versus failed CTO-PCI

All-cause mortality

5 years

Galassi et al.

[36]

1395

75.3%

Successful versus failed CTO-PCI

Cardiac mortality, MACE

Median 24.7 months

Valenti et al.

[37]

Multi-center registry of retrograde approach Single-center study

486

71%

Successful versus failed CTO-PCI

Cardiac survival

Median 2 years

Claessen et al.

[14]

Multi-center registry

1734

71.1% in LAD, 69.1% in LCX, 65.1% in RCA

Successful versus failed CTO-PCI

Mortality

1178 days

Safley et al.

[38]

Single-center study

2608

77% in LAD, 76% in LCX, 72% in RCA

Successful versus failed CTO-PCI

Survival

5 years

Results Successful CTO-PCI was associated with improved survival, versus failed CTO-PCI (adjusted HR 0.72, HR 0.66 in matched analysis); survival benefit did not differ among epicardial vessels. Successful CTO-PCI independently predicted lower cardiac mortality (HR 0.40), and reduced need for CABG (HR 0.21), versus failed CTO-PCI. Successful CTO-PCI was associated with lower mortality, and reduced need for CABG, versus failed CTO-PCI; insulindependent diabetes independently predicted mortality. Failed CTO-PCI was associated with higher MACE, versus successful CTO-PCI at both time points; a high perforation rate was observed in those with failed procedure (25%). Successful CTO-PCI was associated with lower adjusted MACE, versus failed CTO-PCI. Successful CTO-PCI independently predicted lower all-cause mortality, versus failed CTO-PCI (adjusted HR 0.32, HR 0.28 in matched analysis). Successful CTO-PCI was associated with lower cardiac mortality and other MACE, versus failed CTO-PCI. Successful, CTO-PCI was associated with improved cardiac survival; benefit was seen in patients with multi-vessel disease, but not in those with single-vessel disease. Successful, CTO-PCI was associated with lower mortality, versus failed CTO-PCI, in LAD, and LCx, but not in RCA territory. Successful, CTO-PCI was associated with improved survival, versus failed CTO-PCI, in LAD, but not in LCx, or RCA territory.

CABG, coronary artery bypass grafting; CTO, chronic total occlusion; HR, hazard ratio; LAD, left anterior descending artery; LCx, left circumflex artery; MACE, major adverse cardiac events; PCI, percutaneous coronary intervention; RCA, right coronary artery.

Studies comparing CTO-PCI versus medical treatment In three studies comparing CTO-PCI versus optimal medical treatment, mortality was comparable between the two strategies at long-term follow-up, in adjusted analysis [44–46]; in one study, the composite of death or MI was lower with CTO-PCI, versus medical treatment [44]. In a report that compared the outcome of CTO revascularization (by CTO-PCI or CABG) versus medical treatment in patients with well-developed collaterals, revascularization was associated with lower MACE, and cardiac mortality at long-term follow-up, in both unadjusted and adjusted analysis [47]. The presence of a ‘true’ comparison group (medical treatment) in these studies enhances the reliability of the results (Table 5). However, the small sample size in all such studies

remains an issue; we cannot rule out type II statistical error as a cause of failure to detect a significant difference in outcome. Meta-analyses of the long-term cardiovascular outcome Meta-analyses demonstrated that successful, versus failed, CTO-PCI was associated with a significant reduction of all-cause mortality [31,48–50], both at short- and long-term follow-up [49], along with reduction of the need for CABG [48,50], and reduction of MACE [50] (Table 6). These meta-analyses had several limitations. Some meta-analyses included studies that used balloon angioplasty only [31,48]; the results of such studies cannot be extrapolated to the contemporary era of advanced stent technology and use of aggressive antithrombotic therapy. In one meta-analysis, the

Please cite this article in press as: Karjalainen PP, Nammas W. Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence. J Cardiol (2017), http://dx.doi.org/10.1016/j.jjcc.2016.12.006

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Table 4 Studies that demonstrated comparable cardiovascular outcome with successful versus failed CTO-PCI. Study

Ref.

Center

de Labriolle et al.

[39]

Single-center study

Jolicœur et al.

[40]

CERDO-Kyoto Registry cohort-2

No. of patients

Success rate

Comparison groups

Endpoint

Follow-up duration

172

73.8%

Successful versus failed CTO-PCI

Composite of cardiac death or non-fatal MI

2 years

Multi-center study

1602

62%

Successful versus failed CTO-PCI

Event-free survival

Median 5.6 years

[3]

Multi-center registry

1524

78.2%

Successful versus failed CTO-PCI

Cardiac mortality, all-cause mortality

3 years

Jaguszewski et al.

[41]

Multi-center registry

1110

66%

Successful versus failed CTO-PCI

All-cause mortality

3 years

Borgia et al.

[18]

Single-center study

302

78%

Successful versus failed CTO-PCI

Cardiac death

4 years

Ciec´wierz et al.

[20]

Single-center study

276 (1:1 matched pairs)

Successful versus failed CTO-PCI

Composite of death or MI

6 months and 2 years

Lee et al.

[42]

Single-center study

333

75.4%

Successful versus failed CTO-PCI

MACE

Median 1317 days

Lee et al.

[43]

Multi-center study

1173

85.6%

Successful versus failed CTO-PCI

All-cause mortality, composite of death and MI

Median 4.6 years

Results No difference in the composite of cardiac death or non-fatal MI was seen between patients who underwent successful, versus failed, CTO-PCI. Successful CTO recanalization was not associated with better eventfree survival (HR 0.90, 95% CI 0.64–1.25), even after adjusting sensitivity analysis. Successful CTO-PCI was associated with lower cardiac mortality but not all-cause mortality; after adjusting for confounders, both endpoints were comparable between the two groups. All-cause mortality was comparable at 3 years in those who underwent successful and failed CTO-PCI, in both unadjusted and propensity score-adjusted analysis. Failed, versus successful, CTO-PCI was associated with more frequent cardiac death in unadjusted analysis, but not after propensity score adjustment. Composite of death or MI was comparable between the two groups at 6-month and 2-year follow-up. No significant difference in MACE between successful and failed CTO-PCI, in both crude and adjusted analysis. Successful, versus failed, CTO-PCI was associated with comparable rates of all-cause mortality (HR 1.04, p = 0.92), and composite of death and MI (HR 1.05, p = 0.89).

CTO, chronic total occlusion; HR, hazard ratio; MACE, major adverse cardiac events; MI, myocardial infarction; PCI, percutaneous coronary intervention.

Table 5 Studies comparing medical treatment versus CTO-PCI. Study

Ref.

No. of patients

Success rate

Ladwiniec et al.

[44]

294 matched pairs

60.2%

CTO-PCI versus medical treatment

All-cause mortality, composite of death or MI

5 years

Yang et al.

[45]

533 matched pairs

79.2%

CTO-PCI versus medical treatment

Cardiac death

Median 45.8 months

Hwang et al.

[46]

435 patients with single CTO

CTO-PCI versus medical treatment

MACE, cardiac death

Median 47.6 months

Jang et al.

[47]

738 patients with Rentrop 3 collaterals

Revascularization by CTO-PCI or CABG versus medical treatment

MACE, cardiac death

Median 42 months

80.1%

Comparison groups

Endpoint

Follow-up duration

Results CTO-PCI, versus medical treatment, was associated with comparable all-cause mortality (p = 0.052), and lower composite of death or MI (p = 0.043). CTO-PCI, versus medical treatment, was associated with comparable cardiac death. CTO-PCI, versus medical treatment, was associated with comparable MACE in unadjusted and propensity score-matched analysis,and comparable cardiac death in matched analysis. Revascularization, versus medical treatment, was associated with lower MACE, and cardiac death; both persisted after propensity score matching.

CABG, coronary artery bypass grafting; CTO, chronic total occlusion; MACE, major adverse cardiac events; MI, myocardial infarction; PCI, percutaneous coronary intervention.

Please cite this article in press as: Karjalainen PP, Nammas W. Percutaneous revascularization of coronary chronic total occlusion: Toward a reappraisal of the available evidence. J Cardiol (2017), http://dx.doi.org/10.1016/j.jjcc.2016.12.006

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JJCC-1443; No. of Pages 9

authors adopted the fixed-effect model, rather than the randomeffects model, for analysis of outcome endpoints, despite the nonuniform distribution of effect sizes [49]. Moreover, in two metaanalyses, substantial heterogeneity existed among the included studies, for analysis of the index outcome [31,50].

Analyses were performed by the random-effects model.

Reappraisal of the quality of evidence

CABG, coronary artery bypass grafting; CI, confidence interval; CTO, chronic total occlusion; MACE, major adverse cardiac events; OR, odds ratio.

Range from 1 to 10 years Long-term mortality Successful versus failed CTO-PCI 15,432 27 [31] Hoebers et al.

2015

[50] Khan et al.

2013

23

12,970

Successful versus failed CTO-PCI

All-cause mortality, MACE, need for CABG

Significant reduction of all-cause mortality at short-term (OR 0.218, 95% CI 0.095–0.498) Significant reduction of all-cause mortality at long-term (OR 0.391, 95% CI 0.311–0.493) Significant reduction of all-cause mortality (OR 0.54, 95% CI 0.45–0.65) Significant reduction of MACE (OR 0.70, 95% CI 0.60–0.83) Significant reduction of need for CABG (OR 0.25, 95% CI 0.21–0.30) Significant reduction of long-term mortality (OR 0.52, 95% CI 0.43–0.62) 30 days (short-term), and 1 year (long-term) Mean 3.7  2.1 years All-cause mortality at short- and long-term 3932 (short-term), 6403 (long-term) 13 [49] Pancholy et al.

2013

7288 13 [48] Joyal et al.

2010

Successful versus failed CTO-PCI

Significant reduction of all-cause mortality (OR 0.56, 95% CI 0.43–0.72) Significant reduction of need for CABG (OR 0.22, 95% CI 0.17–0.27; 10 studies) Weighted average 6 years All-cause mortality, need for CABG Successful versus failed CTO-PCI

Results Follow-up duration Endpoint Comparison groups No. of patients No. of studies Publication year Ref. Study

Table 6 Meta-analyses of studies comparing successful versus failed CTO-PCI.

No significant heterogeneity (both endpoints). Results of sensitivity analyses were not reported. Analyses were performed by the random-effects model. Assessment of study validity was not stated. Low heterogeneity was observed for both outcome endpoints. Analyses were performed by the fixed-effects model. Analyses were performed by the random-effects model.

P.P. Karjalainen, W. Nammas / Journal of Cardiology xxx (2017) xxx–xxx

Remarks

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The main issue of the available evidence for a clinical benefit of CTO-PCI is the lack of randomized controlled trials that compare the efficacy and safety of PCI versus an alternative strategy (optimal medical treatment or CABG). Randomized controlled trial is the ‘gold standard’ study design for comparison of two alternative strategies, since it guarantees equal chance for each patient to receive either one of the alternatives; moreover, it is conducted prospectively under standardized conditions which minimize the influence of confounders. Most of the available evidence for a potential clinical benefit of CTO-PCI derives from observational studies: some of which are single-center, many are small-sized, and most are based on retrospective analysis of data, whether these data were collected prospectively or not; evidence derives also from some large registries. Comparison of outcome between alternative approaches in observational studies (and registries) is often limited by selection bias, even in studies reporting adjusted (or propensity score-matched) analysis that accounts for possible ‘measurable’ confounders; no adjustment however meticulous could account for ‘immeasurable’ confounders, such as operator’s discretion, operator’s experience, patient’s preference, and others. Moreover, meta-analyses suffer important limitations either: most importantly is that they did not include randomized studies; another limitation is significant heterogeneity of the included studies due to differences in cohort size, definition of CTO, CTO location, definition of success, imaging modality, follow-up duration, and not least, old data (when techniques and equipment were limited). Another equally important concern is that most of the available observational studies compared the outcome of successful versus failed CTO-PCI, rather than comparing the outcome of a whole CTO-PCI cohort (with all successful and failed procedures) versus a ‘true’ control cohort (alternative strategy); evidence derived from such comparison is questionable for many reasons. First, there is no evidence that the failed CTO-PCI group received optimal medical treatment; therefore, it cannot adequately serve as a ‘conservative’ control group. Second, the baseline characteristics of such group are often unmatched with (often worse than) the successful group [16]; worse baseline risk profile could have determined procedural failure as well as worse long-term outcome, alike. Interestingly, in many studies, no difference in clinical outcome was observed between the two groups (successful versus failed CTO-PCI) after adjusted analysis [3,18,20,39–43]. Third, failed procedures were associated with a high complication rate; indeed, the repeated attempt at passing wires and balloons across occluded segments is accompanied by substantial trauma; this could translate into higher procedural and in-hospital complications. In a weighted meta-analysis (65 studies, 18061 patients, 77% pooled success rate), failed procedures were associated with significantly higher rates of in-hospital death, perforation, and tamponade [15]. In a more recent meta-analysis (25 studies, 16490 patients, 77% pooled success rate), failed procedures were associated with significantly higher rates of in-hospital death, in-hospital MACE, in-hospital MI, perforation, tamponade, and more need for urgent CABG [51]. In the large multi-center registry by Mehran et al., high rates of coronary dissection and perforation were reported with failed procedures (9.4% and 7.4%, respectively) [16]. In two recent studies, periprocedural myocardial injury sustained during CTOPCI was associated with reduced MACE-free survival at long-term

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follow-up [52,53]. No wonder that procedural failure was an independent predictor of worse clinical outcome in two large multi-center studies [35,36]. The worse long-term outcome of patients with failed procedures could have been determined by the higher procedural and in-hospital complication rate, and thus could be iatrogenic from the PCI procedure. Finally, patients who underwent successful procedures with stent implantation receive long-term effective dual antiplatelet therapy; no information on whether such therapy was equally received by patients who underwent failed procedures; it is well known that dual antiplatelet therapy improves survival of patients with coronary artery disease. Indeed, procedural success, versus failure, might be influenced by operator bias. In one study, the objective parameter of successful guidewire crossing within 30 min was adopted as an endpoint, instead of actual procedural success [54]. Long-term patency has also been questioned: in a small multi-center study (n = 100) that employed the subintimal tracking and reentry technique as a bailout strategy for failed CTO-PCI by the conventional techniques, angiographic follow-up (72%) revealed restenosis in 25%, and re-occlusion in 12.5% [55]. On the other hand, in three recent studies that compared CTO-PCI with a ‘true’ control group that received optimal medical treatment, long-term mortality was comparable between the two strategies after propensity score-matched analysis [44–46]. The Italian Registry of Chronic Total Occlusion reported that more than two-thirds of patients with CTO had MVD [5]. Additionally, in The Canadian Multicentre CTO Registry, MVD was present in 76% of patients with CTO: in single-vessel CTO, 47% occur in the right coronary artery, 20% in the left anterior descending artery, 16% in the left circumflex territory [1]. In the calculation of the SYNTAX score for patients with MVD, the weight given to the presence of CTO is such that most of these patients would qualify for CABG (score 23), according to the last update of the European Society of Cardiology guidelines on myocardial revascularization [56]. Interestingly, in a post hoc analysis of the SYNTAX trial (n = 1800), nested PCI (n = 198), and nested CABG registries (n = 649), complete revascularization to patients with 1 CTO (PCI: 26.3%, CABG: 36.4%) was achieved more frequently in the CABG versus PCI group (68.1% versus 49.4%, p < 0.001); in the same report, incomplete revascularization was associated with higher 4year mortality in the whole cohort, as well as in the subgroup with CTO [57]. On the other hand, in patients with a single-vessel CTO, successful, versus failed, CTO-PCI was not associated with a longterm survival benefit [37,41]. Individually, survival benefit associated with successful, versus failed, CTO-PCI was consistent in the left anterior descending artery, but not in the left circumflex territory; lack of benefit was consistent in the right coronary artery [14,33]. Both the current European and American guidelines on PCI have given class IIa recommendation (level of evidence B both) for percutaneous revascularization of CTO [56,58]. Moreover, the Appropriate Use Criteria for coronary revascularization downgraded the recommendation of CTO-PCI, compared with PCI for stenotic non-CTO lesions in several clinical scenarios [59]. Other concerns to be considered include the high cost of dedicated equipment, the lengthy procedure times, with inevitable greater radiation exposure, and excessive use of contrast medium with the potential risk of contrast-induced nephropathy in patients with frequent comorbidities. Solid evidence is awaited from ongoing randomized controlled trials comparing CTO-PCI versus optimal medical treatment: three trials are underway. The EURO-CTO trial (NCT01760083) will explore quality of life parameters at 12 months, and clinical endpoints at 3 years. The DECISION-CTO (NCT01078051) will examine cardiac mortality and MI at 5 years. The EXPLORE trial will compare a strategy of CTO-PCI versus medical treatment in patients with a non-infarct-related artery CTO who underwent primary PCI: the primary endpoints are left

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