The purpose of the COMPLEX Registry is to prospectively and retrospectively collect baseline, clinical and procedural data of patients who have undergone PCI or CABG for complex and/ or calcified chronic CAD, irrespective of clinical presentation as well as to prospectively collect data about their clinical outcomes. The outcomes will be compared in different clinical subgroups (e.g. PCI vs. CABG). The impact of current PCI techniques/ devices, but also CABG strategies in different clinical settings and coronary artery lesions on cardiovascular outcomes will be assessed.

a. PCI cohort - Periprocedural outcomes/ complications to be analyzed represent: final result (e.g. TIMI flow), stent expansion, dissections, perforations, and prevalence of thrombus (assessed by angiography and intravascular imaging) b. CABG cohort - Periprocedural outcomes/ complications to be analyzed include: final result (e.g. graft flow), number and type of grafts, total length of surgery, bypass time, cross-clamp time, median chest-tube output (mL), bleeding, duration of CCU/ ICU stay, re-operation.

c. For the PCI, CABG as well as medically managed cohort, short and long-term clinical outcomes of interest include: unstable angina (UA), stent-/scaffold thrombosis, target lesion failure (TLF), target vessel revascularization (TVR), ischemia driven revascularization, repeat hospitalization, new/worsening heart failure, cardiogenic shock, stroke, bleedings, cardiovascular death and all-cause death.

2. PCI cohort:

1. To describe procedural and clinical performance of various PCI devices including high pressure balloons, scoring, balloons, cutting balloons, rotational atherectomy, orbital atherectomy, intravascular lithotripsy, stent and scaffold devices implanted in patients presenting with complex and calcified chronic CAD
2. To study the impact of different PCI devices and revascularization strategies used for lesion preparation and PCI optimization strategies among patients undergoing PCI
3. To describe early and late angiographic and OCT-findings among complex and calcified coronary artery disease patients treated with various metallic stent and scaffold devices
4. To assess possible predictors for coronary stent implantation or device failure 3. CABG cohort:

a. To describe procedural and clinical performance of various surgical techniques b. To assess outcomes across various surgical cohorts (e.g. urgent vs. elective, diabetic vs. non-diabetic, gender disparities) c. To investigate various CABG revascularization strategies (e.g. off- versus on-pump, "Fully arterial", minimal invasive approach) and their impact on short and long-term outcomes d. To describe perioperative recovery and risk for in-hospital complications (e.g. wound infections, pneumonia) e. To assess possible predictors for graft failure with contemporary surgical techniques 4. Conservative - only medically treated - cohort:

1. To describe medical management (drugs regimens) as well as other lifestyle interventions in patients presenting with complex and calcified chronic CAD who are being treated with a primarily conservative (non-invasive) strategy.

2. To study the clinical impact of different treatment strategies/ medical regimens used among chronic, complex CAD, which are being managed solely with medical therapy.

3. To assess possible predictors for management failure (e.g. recurrence of symptoms or impaired quality of life).

   5. To compare presentation, (medical) management, short- and long-term outcomes across the different treatment cohorts (PCI, CABG and medically managed cohort).

   6. To specifically describe age- and gender-specific disparities across the various treatment regimens (e.g. PCI versus CABG).

   7. To evaluate the impact of different antithrombotic regimens on patient's clinical outcomes 8. To study procedural and clinical outcomes among CAD patients requiring hemodynamic support using mechanical devices.

   9. To analyze the performance of various non-invasive testing modalities (e.g. laboratory/ ECG parameters, treadmill-test, stress-echocardiography, CMR, SPECT or PET-CT) in order to predict outcomes of patients with chronic, complex CAD.

   10. To describe economic implications (cost-effectiveness) of various interventional treatments for CAD.

Inclusion Criteria:

• Subject >18 years of age
• Individuals presenting with chronic, complex and/or calcified CAD and requiring PCI or CABG
• Complex coronary artery disease / lesions must include at least one of the following attributes:
• Long and/ or heavily calcified coronary lesions
• In-stent restenosis
• Chronic total occlusions (CTO)
• Left main lesions
• Bifurcation lesions
• Bypass graft lesions
• Small vessel disease / coronary microvascular dysfunction (e.g. not amenable to PCI)
• Subjects must be willing to sign a patient informed consent (PIC) or must have signed the General Consent (GK).

Exclusion Criteria:

The presence of any one of the following exclusion criteria will lead to exclusion of the patient.

• Patient is <18 years of age
• Patient unwilling or unable to provide informed consent
• Patients with no complex and calcified CAD

In an all-comers design, virtually any CAD patient with complex and/ or calcified coronary artery disease treated with PCI or CABG at the Heart Center of the Luzerner Kantonsspital (LUKS) and giving consent may be included.