European Journal of Cardiovascular Medicine

Chronic total occlusion represents a complete coronary arterial obstruction with TIMI grade 0 flow and a duration of at least three months. CTOs are frequently encountered in patients undergoing coronary angiography and  contribute substantially to myocardial ischemia, angina, impaired ventricular function and reduced quality of life. Successful CTO recanalization has been associated with improvement in anginal symptoms, quality of life, ventricular function  and reduction in subsequent revascularization requirements[1,2].

Despite advances in contemporary interventional cardiology, CTO-PCI remains one of the technically demanding forms of coronary intervention. Long occlusions, severe calcification, tortuosity, ambiguous proximal caps, distal vessel characteristics and previously stented segments can complicate guidewire crossing and subsequent balloon or stent delivery[3]. Contemporary CTO strategies therefore rely on careful selection of guidewires, support catheters, microcatheters, balloons, stents and antegrade or retrograde techniques.

Microcatheters have an important technical role in CTO-PCI. They provide support for guidewire manipulation, facilitate guidewire exchange, permit controlled redirection of the wire and assist with advancement through complex or tortuous anatomy. Their importance has been particularly emphasized in challenging antegrade and retrograde CTO procedures. However, microcatheters are not universally required for every lesion[4,5]. They increase procedural equipment requirements ,cost and may themselves be difficult to advance or retrieve in highly tortuous or calcified anatomy.

The choice of whether to use a microcatheter is therefore dependent on several factors, including lesion morphology, guidewire characteristics, operator experience, available equipment and the need for guidewire exchange. An important clinical question is whether selected CTO lesions can be successfully treated using alternative guidewire and balloon strategies without routine microcatheter use[6-9].

The present study examined CTO-PCI procedures performed at PNS Shifa Hospital, Karachi, between 2018 and 2024. It compared procedures performed with and without microcatheters , assessed procedural characteristics, operator experience, equipment selection,pre- and post-intervention coronary findings. The study therefore provided a real-world description of equipment utilization and procedural outcomes in a CTO-PCI population.

Objectives

The primary objective was to compare procedural outcomes of CTO-PCI performed with and without microcatheter use. The secondary objectives were to describe the demographic , clinical characteristics of patients undergoing CTO-PCI, to determine the frequency of microcatheter and non-microcatheter CTO-PCI, to describe CTO anatomical distribution and procedural access routes, to characterize the guidewires, balloon catheters and stents used during CTO intervention It aso focus to assess the relationship between operator experience and procedural equipment selection, to compare pre- and post-dilation coronary findings according to microcatheter use and to evaluate whether procedural characteristics were associated with statistically significant differences in outcomes.

This was a retrospective observational secondary data analysis conducted using CTO-PCI records from PNS Shifa Hospital, Karachi, Pakistan, including procedures performed over a six-year period from 2018 through 2024. The source dataset contained detailed clinical and procedural information from CTO interventions. The study population consisted of adult patients aged 18 years or older who underwent CTO-PCI during the study period, with a total of 122 eligible patients included in the final analysis. The extracted variables included age and demographic characteristics, diabetes mellitus, hypertension, ischemic heart disease ,other comorbidities, CTO anatomical location, arterial access route, microcatheter use, guidewire type, balloon catheter type and size, stent type and dimensions, POBA and PCI, double-stick technique, operator experience, pre-dilation lesion status, post-dilation residual disease,  procedural complications and outcomes. Procedural success was defined as successful CTO recanalization with TIMI grade 3 flow without complications such as vessel perforation, dissection, guidewire entrapment or conversion to open surgery.

Inclusion criteria

·         Age ≥18 years.

·         Underwent CTO-PCI during 2018–2024.

·         Availability of relevant procedural records.

·         Documentation sufficient for assessment of the study variables.

Exclusion criteria

Patients were excluded when records were incomplete, relevant entries were missing or follow-up information was insufficient for secondary analysis.

Ethical considerations

The study received institutional ethical approval from the Institutional Review Board of PNS Shifa, Karachi. The analysis used de-identified retrospective data; therefore, individual patient consent was waived. Confidentiality was maintained according to institutional requirements.

A total of 122 patients who met the inclusion  were included in this retrospective analysis of secondary data collected between 2018 and 2024. The number of CTO-PCI procedures varied across the study period  with the highest number recorded in 2023 (45, 36.9%), followed by 2022 (26, 21.3%).

The majority of patients were aged 51–70 years, including 35.25% aged 51–60 years and 31.97% aged 61–70 years. Hypertension, diabetes mellitus  and ischemic heart disease were among the documented comorbidities alongside previous myocardial infarction, angina, multivessel coronary artery disease, and chronic kidney disease.

These characteristics indicate a predominantly middle-aged and older population with a substantial burden of cardiovascular disease.

Table 1. Types of Balloon Catheters Used During CTO Intervention (n = 122)

Table 1 summarizes the types of balloon catheters used in 122 patients, categorized by balloon diameter and length. Crossway 2.0 × 15 mm was the most frequently used balloon catheter, accounting for 45.08% of cases, followed by NC Sapphire 2.75 × 15 mm, which was used in 13.11% of cases. NC Sapphire accounted for 9.82% of balloon catheter use. These findings indicate that Crossway 2.0 × 15 mm was the predominant balloon catheter used during the procedures.

Most Common Guidewires utilized among 122 patients were JR-4.0 (36.07%) and XB-3.0 (46.72%). 32.79% of patients received three guidewires’ combinations such as combinations of AL-1, JR-3.5, and XB-3.0 as compared to other combinations of wire (Table 02)

Table 2: List of all type of Guide Wire used for the CTO intervention

Right radial artery access was the predominant approach, used in 110 patients (90.16%). The RCA was the most frequent CTO location (61, 50.0%), followed by the LAD (26, 21.31%) and LCX (13, 10.65%). Microcatheters were used in 10 procedures (8.2%), while 112 (91.8%) were performed without documented microcatheter use. XB-3.0 and JR-4.0 were the most frequently reported guidewires, accounting for 46.72% and 36.07%, respectively. Crossway 2.0 × 15 mm was the most frequently reported balloon catheter (45.08%). Xience Xpedition was among the commonly documented stent platforms, and 30 patients (24.6%) reportedly received combinations of two stent types. Multiple guidewires, balloons, and stents could be used during an individual procedure; therefore, device-specific percentages are not necessarily mutually exclusive.

Table 3. Summary of anatomical, access, and device-related variables

Most patients underwent PCI involving stent implantation or additional interventional treatment rather than POBA alone. The dataset recorded 22 patients (18.03%) with balloon-based treatment, including drug-eluting balloon (DEB) applications, while 100 patients (81.97%) were recorded without POBA. DEBs were used in different coronary territories, including the RCA, LAD, and posterior descending artery (PDA), with 3.28% of cases reportedly involving multiple coronary sites. The LAD was the most frequently reported PCI target in the supplied procedural summary, although the reported territory-specific percentages require verification.

Intraprocedural anticoagulation was documented primarily with unfractionated heparin. A dose of 10,000 units was administered in 77 patients (63.11%), followed by 12,500 units (9.84%) and 7,500 units (7.37%). Other pharmacological therapies relevant to CTO-PCI include dual antiplatelet therapy (aspirin), high-intensity statin therapy, and additional cardiovascular medications according to the patient's clinical condition

Table 4. Summary of interventional treatment and documented Heparin therapy

Antiplatelet therapy is used to prevent thrombotic complications, while statins reduce atherosclerotic cardiovascular risk. The choice and duration of antiplatelet treatment depend on stent implantation, bleeding risk, and clinical presentation. Heparin dosing should be assessed alongside body weight, activated clotting time and procedural duration.

The secondary analysis examined immediate procedural findings and associations between procedural variables and operator categories. An excellent result with no residual disease was reported in 120 of 122 patients (98.36%), while one patient had a lesion recorded as unchanged or untreated. Another patient had a separately documented excellent LAD result. These findings suggest a high rate of favorable immediate procedural results; however, the original records should be checked to establish whether these categories are mutually exclusive and whether the outcome refers specifically to the treated CTO lesion or to all coronary vessels.

Table 5. Summary of  immediate procedural outcomes

The inferential analysis evaluated microcatheter use, balloon type, stent type, vascular access, double-stick technique, CTO location, POBA, and PCI across primary, secondary, and additional operators. Stent type had a p-value of 0.0051 for primary operators, compared with 0.3038 for secondary operators and 0.8905 for additional operators. The remaining comparisons did not demonstrate statistically significant associations at the conventional 0.05 threshold.

The results demonstrate that CTO-PCI was performed predominantly through radial access in a population with frequent cardiovascular comorbidities, with the RCA being the most commonly treated CTO vessel. The high reported rate of excellent immediate results is encouraging, but a comprehensive assessment of procedural effectiveness requires additional clinical outcomes.

In this 122-patient CTO-PCI cohort, procedures were concentrated in 2022–2023, the RCA was the predominant CTO location, right radial access was the most common approach, and unfractionated heparin was the principal documented intraprocedural anticoagulant. Most patients were reported to have favorable immediate procedural results. Further verification of outcome definitions, medication records  and the statistical significance threshold is necessary before drawing conclusions about comparative efficacy, operator performance or long-term clinical benefit

To assess the relationship between operator experience, the use of microcatheters, balloon types, stent types, and procedural outcomes, two-way ANOVA was applied with an alpha level of 0.05 to evaluate the significance of the results across these variables. There was no statistically significant difference in outcomes when microcatheters were used versus not used during the procedures (p = >0.05).

Table 6: Comparative Analysis of using Micro Catheters, Balloon & Stent Type, and

Procedure with Operator Experience

Inferential analysis of procedural factors in CTO-PCI revealed no statistically significant differences in stent selection by secondary or additional operators (p > 0.05). Similarly, no significant associations were observed between procedural outcomes and vascular access routes, double-stick technique, CTO location, or POBA across operator experience levels (p > 0.05). Chi-square analysis also demonstrated no statistically significant difference in pre- or post-dilation outcomes between procedures performed with and without microcatheters (p > 0.05), indicating comparable dilation outcomes in both groups.

Table 7: Comparative analysis of using Micro Catheters, and Non Micro Catheter with

the post pre and post dilation status.

This retrospective secondary analysis provides a real-world description of CTO-PCI practice over a six-year period and specifically examined the relationship between microcatheter use and procedural outcomes. The most prominent finding was that microcatheter use was relatively infrequent in this dataset, with approximately 92% of CTO procedures performed without a microcatheter. Despite this marked difference in equipment utilization, the recorded post-intervention outcomes were favorable, with 120 of 122 patients reported to have no residual disease.

Microcatheters have long been considered essential in chronic total occlusion percutaneous coronary intervention (CTO-PCI), particularly for navigating difficult lesions, manipulating guidewires, and facilitating equipment exchange. Their use has been associated with improved procedural success in complex CTO cases. Brilakis et al. emphasized the importance of microcatheters in improving guidewire control during antegrade and retrograde approaches and facilitating device exchange in complex coronary anatomy (9).

Similarly, Kandzari et al. reported a success rate of 73% in a study involving 163 CTO patients, in which microcatheters were used in 91.7% of cases, highlighting their potential value in managing complex lesions (10). However, the present study found no statistically significant difference in procedural outcomes between cases in which microcatheters were used and those in which alternative techniques were employed (p = 0.4565).

Operator experience plays a pivotal role in determining procedural success in CTO-PCI, as demonstrated by several large-scale studies. The present study also identified a statistically significant difference in stent selection by primary operators (p = 0.0051), suggesting that operator-related factors may influence procedural decision-making and equipment selection.

The choice of access route in CTO-PCI has been widely debated, with increasing adoption of radial access in recent years. Radial access is associated with fewer bleeding and vascular complications than femoral access. However, the present study found no statistically significant difference in procedural outcomes between radial and femoral access routes (p = 0.2995), suggesting that both approaches may be appropriate depending on lesion complexity, patient characteristics, and operator preference. Similar findings were reported by Kinnaird et al., who analyzed more than 26,000 CTO-PCI procedures and found that femoral access was associated with higher rates of major bleeding, access-site complications, and in-hospital mortality, supporting the safety advantages of radial access (13).

Another important procedural consideration in CTO-PCI is the use of enabling strategies, including the double-stick technique and appropriate balloon catheter selection. These strategies are often necessary in complex CTO cases requiring multiple crossing techniques or specialized devices. An analysis of approximately 2,800 cases from the British Cardiovascular Intervention Society database demonstrated improved CTO-PCI success with the use of multiple enabling strategies, reporting an 83.8% success rate when three or more strategies were employed (14).

In contrast, the present study found no statistically significant differences in procedural outcomes according to the use of the double-stick technique (p = 0.7878) or the type of balloon catheter used (p = 0.4849). These findings suggest that the effectiveness of individual procedural strategies may depend on lesion characteristics, procedural complexity, and operator expertise.

CTO-PCI is associated with greater procedural complexity and a higher risk of adverse events than non-CTO PCI. Reported complications include coronary perforation, myocardial infarction, and vascular complications. A meta-analysis involving more than 28,000 patients reported coronary perforation and other significant procedural complications, with coronary perforation rates generally ranging from 1% to 2% (15). Advances in microcatheter technology, including improved deliverability and resistance to deformation, have further enhanced their utility in challenging coronary anatomies (16).

Despite these technological advances, the present study found no statistically significant difference in procedural outcomes between cases involving microcatheter use and those without microcatheters (p = 0.4565). This finding suggests that alternative techniques may also achieve favorable outcomes in selected cases. Liu et al. (2018) reported improvements in left ventricular ejection fraction following PCI associated with microcatheter use, although their findings should be interpreted in the context of the specific patient population and outcomes evaluated (17).

Wilson et al. also highlighted the potential advantages of specialized microcatheter designs, including locking microcatheters, for navigating tortuous coronary anatomy, although these devices are not essential in every CTO-PCI procedure (18). Kinnaird et al. reported improved procedural success with the use of enabling strategies, including microcatheters, while also highlighting the potential for increased complications, such as coronary perforation, when multiple specialized devices are employed (14). Similarly, Kandzari et al. demonstrated the value of microcatheters in guidewire recanalization during complex CTO procedures, supporting their role as an important but not universally indispensable procedural tool (10).

Strengths of the Study

Several features strengthen the clinical relevance of this analysis.

1. Real-world CTO-PCI data: The study reflects actual interventional practice at a specialized cardiac center rather than a simulated procedural environment.

2. Six-year observation period: Data from 2018–2024 provide a relatively broad temporal window for describing CTO-PCI practice.

3. Detailed procedural variables: The dataset included access route, guidewire, balloon, stent, microcatheter, lesion location, and procedural technique.

4. Multiple operator categories: The analysis considered primary, secondary, and additional operator experience.

5. Direct procedural comparison: The study specifically examined CTO-PCI procedures with and without microcatheters.

6. Objective procedural findings: Pre- and post-dilation coronary findings were incorporated into the analysis.

7. Institutional ethical oversight: The study was based on an institutionally approved de-identified retrospective dataset.

Limitations

The findings should be interpreted in light of several methodological limitations.

First, the study was retrospective and observational; therefore, causal relationships between microcatheter use and procedural outcomes cannot be established. Second, the sample size was modest, with only 122 patients. More importantly, only 10 patients underwent microcatheter-assisted CTO-PCI compared with 112 procedures without microcatheters. This substantial imbalance reduces the statistical power of comparisons between groups.

Third, microcatheter selection was likely influenced by lesion complexity, operator preference, guidewire requirements, and procedural circumstances. Consequently, confounding by indication may have influenced the observed association. Fourth, the study was performed at a single center, limiting generalizability to other hospitals, operators, and patient populations.

Although the methodology states that lesion characteristics such as lesion length and calcification were extracted, the presented analysis does not provide sufficiently detailed stratification of outcomes according to these variables. Similarly, the dataset contains information regarding procedural complications, but the available results do not provide a comprehensive complication-rate comparison between the two microcatheter groups.

The study also relies on historical repository data rather than prospective allocation to microcatheter versus non-microcatheter strategies. Therefore, the finding of no statistically significant difference should be interpreted as an observational association rather than evidence of therapeutic equivalence or non-inferiority.

Finally, the original manuscript reports both chi-square and two-way ANOVA analyses using different significance thresholds. Future studies should prespecify the statistical framework, clearly define the primary endpoint, and use multivariable adjustment for important confounders.

Microcatheters are valuable tools in CTO-PCI, particularly in cases involving complex lesions and challenging coronary anatomy. However, the findings of the present study indicate that their use was not associated with a statistically significant difference in procedural outcomes compared with alternative techniques. This suggests that favorable outcomes may also be achieved through appropriate alternative strategies, depending on operator expertise and lesion characteristics. The study further highlights the importance of operator experience, particularly in equipment selection, and the individualized selection of access routes, enabling strategies, and procedural devices. Careful procedural planning, appropriate operator training, and continued technological development may help improve success rates and minimize complications in CTO-PCI.

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