European Journal of Cardiovascular Medicine

The prevalence of coronary artery disease in the general population has increased over time. The traditional modalities of treatment have been revascularization procedures like percutaneous coronary intervention (PCI) and coronary artery bypass grafting (CABG) with the main goals of treatment being increased survival rates and symptom free survival of the patients. CABG has proven to be the treatment of choice especially for the management of complex multi-vessel coronary artery disease.¹ Chronic total occlusion of coronary vessels is a special subset of coronary artery disease presenting with difficulty in preoperative assessment of vessel anatomy and also in surgical revascularization.

Coronary artery chronic total occlusions (CTOs) are defined as 100% coronary occlusions with TIMI (Thrombolysis in Myocardial Infarction) grade 0 flow persisting for >3 months.² Chronic total occlusions despite being commonly encountered have been less often studied. They usually demand greater technical skills whether being managed either with percutaneous coronary intervention (PCI) or via coronary artery bypass grafting (CABG). The anatomic location of CTOs within each coronary artery can be either in the proximal, mid or distal segment.^3,4,5 This may have treatment implications because PCI procedures are in the majority of cases not suitable for distal coronary segments whereas CABG procedures are generally performed in distal coronary segments and hence are able to treat both proximal and distal CTOs. In CTOs, the affected coronary artery is often poorly seen via retrograde filling from collaterals in coronary angiogram. This may lead to uncertainty in assessment of its quality and size and hence may further pose difficulty in choosing the best treatment option. Also, controversy exists in choosing a specific treatment option owing to variations in guidelines for management of CTOs in different parts of the  world. ⁶ We intend to conduct a descriptive study to estimate the incidence of CTOs, the surgical outcomes and post-operative complications in the management of CTOs.

This is a prospective observational study conducted from March 2022.  Data was collected of patients undergoing Coronary artery bypass grafting at NIMS, Hyderabad from March 2022 to December 2022 and was tabulated in MS Excel format. We reviewed 40 cases where Coronary Artery Bypass Grafting was done for patients with chronic total occlusion of one or more coronary vessels and analyzed the surgical outcomes.

 Inclusion Criteria: Adult patients aged between 18-75 years of age, of any gender, undergoing coronary artery bypass grafting for coronary artery disease with chronic total occlusion of one or more coronary vessels.

 Exclusion Criteria: Patients with previous history of CABG, history of previous percutaneous intervention for coronary artery disease, accompanying valvular abnormalities, ischemic ventricular septal rupture and cardiogenic shock.

All data from Case records, i.e., patient demographics, diagnosis, surgeries performed, OT records ,and follow up records were collected and analyzed in excel spread sheet. Continuous data was presented as Mean and Standard Deviation, while categorical data has been presented as percentages.

Table-1: Demographic details of the patients in study

Majority of the patients with coronary artery disease having CTOs of one or more vessels were in the age group of 51-60 years accounting to 17 cases (42%). Males constituted 87.5% (35) of the cases while females constituted 12.5% (5) of cases. CAD having chronic total occlusion of coronary vessels were evaluated for the co-morbidities namely Diabetes mellitus, Hypertension, Dyslipidemia, Chronic Kidney Disease and history of Cerebrovascular accidents. 13 patients had a single co-morbidity, 13 had two co-morbidities. It was noted that 9 patients had no previous history of any single co-morbidity. Of the 13 patients with only a single co-morbidity, 6 had only diabetes mellitus, 6 had only hypertension and 1 had only dyslipidemia. Of the 13 patients with two co-morbidities, 9 had diabetes mellitus and hypertension and 4 had diabetes mellitus and dyslipidemia. Of the 40 patients evaluated, 9 (22.5%) patients had no history of any known co-morbidities.  In all, a total of 23(57.5%) patients had diabetes. Hypertension was seen in 20 patients (50%), while dyslipidemia was noted in 7 patients (17.5%). 4 patients (10%) were suffering from CKD. A total of 27 patients with CTOs, of the 40 evaluated had previous history of smoking, amounting to 67.5% of the cases. 8 patients had presented with the chief complaint of shortness of breath (S.O.B), while 31 patients presented with the complaint of chest pain/discomfort. 24 of them had prior history of MI.

Table-2: Findings of angiogram in present study

Out of 40 patients evaluated in our study, 6 patients had a left ventricular ejection fraction (LVEF) less than or equal to 30% while 34 patients had an ejection fraction more than 30%. 15 patients had disease of the left main coronary artery which constituted 37.5% of the cases. Triple vessel disease(TVD) was observed in 34 patients, accounting to 85% of the cases while double vessel disease(DVD) was observed. Right dominance was observed in 80% of the cases (32 patients), left dominance in 10% of the cases (4 patients) and co-dominance in 10% of the cases (4 patients).

Figure-1: Chronic total occlusion of vessels in present study

Chronic total occlusion of a single coronary vessel was observed in 26 patients, amounting to 65% of the cases while involvement of two vessels with CTOs was seen in 13 patients, accounting to 32.5% of the cases. On patient had CTO of LMCA.

Table-3: Distribution of Chronic total occlusion of vessels in present study

A total of 40 patients with CAD having chronic total occlusion of coronary vessels were evaluated and the vessels in which CTOs were present and their anatomical locations were analyzed. 10 patients had CTO of only LAD, 14 patients had CTO of only RCA.

Table-3: Anatomical Location in present study

In total, CTOs in LAD were found in15 patients, CTOs in LCX were found in 13 patients, CTOs in RCA were found in 24 patients and a single patient had LMCA ostial CTO.

Figure-2: Number of grafts involved in present study

Out of 40 patients studied, a single graft was placed in 1 patient, 2 grafts were placed in 4 patients, 3 grafts in 14 patients, 4 grafts in 17 patients and 5 grafts were placed in 4 patients.

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Table-4: All over outcome after procedure in present study

Of total 40 patients who had undergone CABG, all vessels with CTOs were successfully in 37 patients. Graft could not be placed in a patient with a single CTO in distal RCA, while grafting was unsuccessful in 1 of the 2 vessels with CTOs, in two patients. 10% of the patients, i.e., 4 out of 40 required endarterectomy of coronary vessels.  10% of the patients, i.e., 4 out of 40 required IABP support peri-operatively, while 90% of the patients recovered without any need for IABP support. A total of 40 patients who had CAD with CTOs in one or more coronary vessels and had undergone CABG were evaluated and followed up. One patient had an episode of MI on POD-3 but recovered well and was discharged in stable condition. Two patients had died on POD-1 on account of low cardiac output syndrome post-operatively. A total of 40 patients who had undergone CABG for CAD with CTO of one or more coronary vessels were followed up for a period of 3 months. >10% improvement in LVEF was noted in 7 patients while an improvement of LVEF between 5-10% was noted in 10 patients. 20 patients had no much difference in the LVEF when compared with their pre-operative values. 2 patients had expired post-operatively while 1 patient who had MI post-operatively had a significant fall in LVEF but was symptom free at 3-month follow-up.

Figure-3: Mortality in present study

A total of 40 patients who had CAD with CTOs in one or more coronary vessels and had undergone CABG were evaluated and followed up. 38 patients were discharged in stable condition. 2 patients had died on POD-1 on account of low cardiac output syndrome.

In the present study, the mean age of all the cases was 58.9 years and it was observed that majority of the patients with coronary artery disease having CTOs of one or more vessels were in the age group of 51-60 years accounting to 17 cases (42%), followed by the age group of 61-70 years accounting to 13 cases (33%). The youngest patient from the group was 43 year old while the oldest of all aged 73 years. Banerjee, et al. reported a mean age of 62.8 in their analysis on clinical outcomes in a cohort of patients at the Veterans Affairs North Texas Health Care System to assess the prevalence of coronary CTO in the patients referred for CABG.⁴ Jang WJ et al.⁷ reported a mean age of 61.6 in their screening of patients with at least 1 CTO detected on coronary angiograms. Thus it could be inferred that CTOs are most common in patients in the latter part of 6^th decade and early part of 7^th decade.

Males constituted majority of the cases accounting to 87.5% of the patients in the current study. This finding echoes with similar incidence noted in the study published by Fefer et al.³ wherein males constituted 80% of the cases in their review of patients from the Canadian Multicenter Chronic Total Occlusions Registry. Thus incidence of CTOs seems to be the more common among male patients.

A total of 40 patients with CAD having chronic total occlusion of coronary vessels were evaluated for the co-morbidities namely Diabetes mellitus, Hypertension, Dyslipidemia, Chronic Kidney Disease and history of Cerebrovascular accidents. In all, a total of 23(57.5%) patients had diabetes. Hypertension was seen in 20 patients (50%), while dyslipidemia was noted in 7 patients (17.5%). 4 patients (10%) were suffering from CKD. Jang WJ et al.^7. reported that in their study of 502 patients, a total of 237(47.2%) patients had diabetes. Hypertension was seen in 320 patients (63.7%), while dyslipidemia was noted in 179 patients (35.7%). 40 patients (8%) were suffering from CKD. Banerjee et al⁴. noted a higher incidence of hypertension (89%) and dyslipidemia (84%) in their patients while the incidence of diabetes (52.2%) and CKD (10.2%) was similar to our study. It is to be noted that the incidence of diabetes and CKD was similar in all the three studies.

In our study, of the 40 cases evaluated, 13 patients had a single co-morbidity, 13 had two co-morbidities, and 4 had three co-morbidities and patient 1had four co-morbidities. It was noted that 9 patients had no previous history of any single co-morbidity. A total of 27 patients with CTOs had previous history of smoking, amounting to 67.5% of the cases while 32.5% of the patients were non-smokers.  Fefer et al.³ noted an incidence of smoking among their study population to be around 72% in their review of patients from the Canadian Multicenter Chronic Total Occlusions Registry. However, Banerjee et al⁴. found a higher incidence of smoking of around 84.5% in their study. Smoking could thus be definitely implicated as a strong risk factor for development of CTOs.

 In our study, 31 (77%) patients presented with the complaint of chest pain/discomfort while 8 (20%) patients had presented with the chief complaint of shortness of breath (S.O.B). 1 patient was diagnosed with CAD with CTOs upon routine evaluation. Thus the classical symptom of angina/chest discomfort for coronary artery disease as reported by Silverman & Wooley⁸ remained the most common presentation in patients with CTOs.

Out of 40 patients observed in this study, 24 of them had prior history of MI accounting to 60% of the cases. 40% had no such history. Banerjee et al.⁴ reported prior history of MI in 55.3% of the cases in their analysis on clinical outcomes in a cohort of patients at the Veterans Affairs North Texas Health Care System to assess the prevalence of coronary CTO in patients referred for CABG. Fefer et al³ noted in their review of patients from the Canadian Multicenter Chronic Total Occlusions Registry that 40% of cases had prior history of MI.

Out of 40 patients evaluated in our study, 15% of the patients had a left ventricular ejection fraction (LVEF) less than or equal to 30% which is quite similar to the results elaborated by Fefer et al³. in their review of patients from the Canadian Multicenter Chronic Total Occlusions Registry.

In our study, the average mean left ventricular ejection fraction of the patients was found to be 58.9%. Jang WJ et al⁷. reported a mean LVEF of 56.9 in their screening of patients with at least 1 CTO detected on coronary angiograms. Gannot S et al.⁹, in their study of patients who underwent angiography at the Sheba Heart Center catheterization laboratory, Israel and were referred for and underwent CABG during a 2-year period, reported a mean LVEF of 50% in cases with CTOs.

Out of 40 patients included in our study, it was observed that 15 patients had disease of the left main coronary artery which constituted 37.5% of the cases. Triple vessel disease(TVD) was observed in 34 patients, accounting to 85% of the cases. Similar findings were observed by Banerjee et al.⁴, who reported left main coronary artery in 38.1% of the cases and triple vessel disease(TVD) in 79.9% of the cases.  This emphasizes the fact that CTO of coronaries is a complex form of CAD usually accompanied by TVD and hence better managed with CABG.

In our study, right dominance was observed in 80% of the cases, left dominance in 10% of the cases and co-dominance in 10% of the cases. Banerjee et al.⁴, reported right dominance in 85% of the cases, left dominance in 9% of the cases and co-dominance in 6% of the cases.

 In our study, chronic total occlusion of a single coronary vessel was observed in 26 patients, amounting to 65% of the cases while involvement of two vessels with CTOs was seen in 13 patients, accounting to 32.5% of the cases. On patient had CTO of LMCA. Jang WJ et al.⁷ reported single vessel CTO in 80.3% of their patients, while Gannot S et al.⁹ reported similar finding in 76% of the cases. Jang WJ et al⁷. reported more than 1 CTOs in 19.7% of patients while Gannot S et al⁹. reported it in 24% of cases with CTOs. Thus it could be inferred that, CTO of a single coronary vessel is more common than a multivessel CTO.

In total, CTOs in LAD were found in15 patients (37.5%), CTOs in LCX were found in 13 patients (32.5%), CTOs in RCA were found in 24 patients (60%) and a single patient had LMCA ostial CTO (2.5%). In study published by Gannot S et al⁹, CTOs in LAD were found 33% of cases, CTOs in LCX were found in 34% of cases and CTOs in RCA were found in 60% of cases. In study published by Banerjee et al,⁴ CTOs in LAD were found 27.4% of cases, CTOs in LCX were found in 24.7% of cases and CTOs in RCA were found in 48.3% of cases. It could hence be inferred that CTOs are more common in RCA, while similar incidence of CTOs was found in LAD and LCX in each subset of patients. CTO of LMCA is a rare entity with only a single case reported in all three studies combined.

All CTOs bypassed either a LIMA or a saphenous venous graft were used as conduits in all the patients. Of total 40 patients who had undergone CABG, all vessels with CTOs were successfully in 37 patients. Graft could not be placed in a patient with a single CTO in distal RCA, while grafting was unsuccessful in 1 of the 2 vessels with CTOs, in two patients. Thus in 92.5% of the patients under study, all CTOs were successfully bypassed. Banerjee et al⁴ reported in their retrospective study on 605 consecutive patients, discharged following an uncomplicated CABG that all CTOs could be successfully bypassed in 85.2% of the cases. Gannot S et al.⁹ reported that they could successfully bypass 86% of CTOs in their study. This reaffirms the fact that most of the CTOs could be successfully bypassed by CABG.

Out of 40 patients studied, 3 grafts were placed in 14 patients while 4 grafts were placed in 17 patients. A single graft was placed in 1 patient, 2 grafts were placed in 4 patients, and 5 grafts were placed in 4 patients. A total of 87.5% of the patients needed 3 or more grafts indicating that CTO of coronary vessels is usually a complex entity with involvement of multiple coronary vessels, thus better managed by CABG.

In our study, 10% of the patients, i.e., 4 out of 40 required endarterectomy of coronary vessels. Of these, one patient expired on POD1 while another patient suffered MI postoperatively. Though the requirement of endarterectomy was not often required, with only 10% of the patients needing it, it was associated with poorer outcomes. It is to be noted that, the patients requiring endarterectomy often needed high inotropic support post-operatively. This finding echoes with the observation by Gill et al¹⁰ who reported that, in a series of 74 patients, who had undergone LIMA-LAD anastomosis, around 25 patients needed endarterectomy and was associated with a high inotropic requirement in 25% of the patients and an incidence of MI in 6.7% of the cases post-operatively.

In our study, 10% of the patients, i.e., 4 out of 40 required IABP support peri-operatively. This is quite high when compared to the need for IABP requirement in general population undergoing CABG.  Parissis H et al¹¹. in their study reported that, of 1919 CABG patients operated 80 patients required IABP (4.17%) and the overall mortality of these patients requiring an IABP support was 16 patients (21.2%). Mortality for patients needing IABP was quite high in our study, i.e., 50%, with 2 of these patients dying on POD 1.

A total of 40 patients who had CAD with CTOs in one or more coronary vessels and had undergone CABG were evaluated and followed up. 37 patients (92.5%) were discharged uneventfully. All these patients were followed up for a period of 3 months. >10% improvement in LVEF was noted in 7 patients while an improvement of LVEF between 5-10% was noted in 10 patients, 20 patients had no much difference in the LVEF when compared with their pre-operative values. Two patients (5%) had died on POD-1 on account of low cardiac output syndrome post-operatively. One patient (2.5%) had an episode of MI on POD-3 but recovered well and was discharged in stable condition. Banerjee et al⁴ reported a mortality rate of 7.1%   in their study while Jang et al. reported an incidence of cardiac death to be around 5.9% in the CTO group.⁷

STUDY LIMITATIONS

Limitations of our study are its observational design and also a small sample size. Also, though patients with very severe left ventricular dysfunction were assessed for the viability of myocardium pre-operatively, assessment of viability of the myocardium was not made in all the patients before surgery and hence data could not be reported of the same in toto. The follow up time period was 3 months and long term results are awaited.

Chronic total occlusion of coronary vessels is a special complex subset of coronary artery disease. Its management thus warrants a precise clinical judgement and sound surgical skills for better patient outcomes. Like CAD, it was most frequently seen in males in their sixth decade of life, with smoking being a definite possible risk factor. Chest discomfort was the most common presenting complaint of the patients with CTOs of the coronaries. CTOs were frequently associated with triple vessel disease of the coronary vessels. Thus surgical management of CTOs by CABG seems to be more appropriate as it can provide revascularization of all major coronary territories. CTOs have been more commonly found in the Right coronary artery, with single vessel CTO being more common than multi-vessel CTOs. Peri-operative low cardiac output, requirement of endarterectomy and IABP support were associated with eventful outcomes and were indicators of a poorer prognosis. Majority of the CTOs were bypassed successfully and significant improvement in the left ventricular ejection fraction was noted in most of the patients post-operatively. Despite their variable complex anatomy, most of the CTOs were amenable to revascularization by CABG reiterating the fact that surgery still remains a definitive mode of treatment for complex CAD

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