When we discussed the article on hybrid myocardial revascularization (HMR) on the blog months ago, I never imagined that this topic would generate such interest to warrant the publication of two consensus documents on either side of the Atlantic. The European one, authored by the Cardiovascular Surgery Working Group of the European Society of Cardiology and the Association of Percutaneous Cardiovascular Interventions, is more comprehensive and predominantly cardiology-focused, resembling the methodology used for clinical guidelines development. In contrast, the American document, a more modest initiative by representatives of the Society of Thoracic Surgeons, serves as a review of the current evidence to update the state of the art.

The methodologies of these two works differ significantly. The European document reflects a broader perspective derived from meetings and guideline-style methodologies. The American paper relies on a literature search and evidence aggregation. Despite these differences, they complement each other well. Below, we provide an organized and critical summary of their main messages.

The growing interest in HMR emphasizes its potential to combine the benefits of both treatment strategies: the long-term patency and prognostic impact of internal mammary artery (IMA) to left anterior descending artery (LAD) anastomosis, and the reduced invasiveness of percutaneous treatment for other territories using new drug-eluting stents, which have demonstrated failure rates below 5% within a year compared to 20% for saphenous vein grafts. While this rationale is valid, it tells only part of the story. Despite saphenous vein grafts being the most frequently used conduits, excluding comparisons with other arterial grafts in the evaluation of new stents creates an unfair competition. Indeed, as cited in the European document to confirm this observation, “the benefit of surgery over intervention in non-LAD vessel revascularization is ambiguous.” Fortunately, the tone of the American paper is more moderate and cautious.

Indications for HMR

The American document defines the ideal candidate as someone who would benefit from the advantages of both procedures. Such a candidate would present:

• Tolerance for single-lung ventilation.
• No history of prior thoracic surgery or radiation.
• Left ventricular ejection fraction >30% and tolerance for CO₂ insufflation in the surgical field.
• No contraindication for dual antiplatelet therapy.
• Multivessel coronary disease with a complex LAD lesion and focal, low-complexity lesions in other vessels.
• LAD anastomosis site free from significant calcification or intramyocardial course.
• Well-preserved IMA graft suitability.

The European document provides a detailed list of indications, including the following:

• Patients with two-vessel disease and an LAD lesion unsuitable for intervention: Although multivessel disease often equates to three-vessel disease, the term “multi” includes more than one vessel, and assumptions made for three-vessel disease should apply equally to two-vessel disease, particularly in non-acute contexts. Pathophysiologically, multivessel disease differs significantly from single-lesion disease due to its potential to involve multiple coronary tree vessels.
• Patients with multivessel disease requiring surgery but with contraindications to median sternotomy or limited graft availability: This approach offers a less invasive alternative to achieve complete revascularization. Such “rescue” from surgical contraindications is particularly relevant, as these patients are often referred for complete percutaneous treatment, especially in our setting.
• Patients with multivessel disease and a complex LAD lesion but poor distal beds for surgical treatment in other territories suitable for percutaneous intervention: This indication seems overly forced, as vessels unsuitable for surgery are often unsuitable for intervention. Conversely, the opposite is less frequent. Percutaneous treatment in such cases may increase event rates, ultimately resulting in incomplete revascularization regardless of the therapeutic option chosen. However, this approach maximizes options for attempting complete revascularization and avoids morbidity from harvesting dysfunctional grafts.
• Patients with multivessel disease undergoing primary angioplasty for the culprit lesion, with deferred revascularization of the remaining territories due to surgical anatomy (residual three-vessel disease, left main disease, or equivalent): This may be the most common scenario in our setting, where HMR has often been performed out of practicality rather than purpose.
• Patients with multivessel disease and surgical candidacy but extensive aortic disease precluding complete revascularization using no-touch techniques: This indication is highly limited to cases where complete revascularization is unachievable, considering the high versatility of surgical revascularization.

Both documents advocate for a consensus-based Heart-Team approach to decision-making regarding vessel strategy, timing, and method. The European guidelines expand the concept of hybrid revascularization to include minimally invasive surgical approaches (e.g., MIDCAB, mini-thoracotomy, inferior mini-sternotomy, robotic techniques, with or without cardiopulmonary bypass) for two vessels, leaving a third vessel or even left main disease—once protected—for percutaneous intervention. This opens the door to the use of multiple arterial grafts, maximizing benefits. Some groups routinely revascularize the left-sided coronary tree, often using multiple arterial grafts, leaving the right-sided tree for subsequent percutaneous intervention. By adhering to this philosophy, they essentially follow HMR principles. The American consensus document adopts a narrower definition, almost equating HMR to MIDCAB (or robotic surgery) combined with stents.

Sequential or Simultaneous Treatment

This is one of the most controversial topics, with each document offering a distinct approach. The European document simplifies the matter by defining four scenarios:

1. Non-LAD or unprotected left main (LM) as the most significant lesion: Intervention first, followed by surgery.
2. Unprotected left main disease: Surgery first or simultaneous treatment.
3. LAD and/or LM culprit lesion in the context of non-ST-elevation acute coronary syndrome (NSTE-ACS):Surgery first or simultaneous treatment.
4. NSTE-ACS where the culprit lesion is not in LM or LAD: Intervention first.

The American document includes a more detailed algorithm that integrates both indications and treatment sequence. Notably, it excludes patients with a SYNTAX score >28–30, severe diabetes, youth, or severe left ventricular dysfunction from HMR or intervention, aligning with the European document’s earlier criticism. Subsequently, its recommendations for sequential treatment are similar to those in the European consensus but omit simultaneous treatment during the same procedure. The American guidelines also make an intriguing assumption for cases of LAD disease as the primary or most severe lesion in the context of NSTE-ACS or unstable angina:

• If non-LAD lesions are critical, intervention is recommended within 48–72 hours after MIDCAB to prevent new ischemic events.
• If non-LAD lesions are not critical, intervention may be deferred for 4–6 weeks post-surgery to minimize complications from dual antiplatelet therapy (DAPT).

The sequencing of treatments has profound implications for the need for DAPT and its associated hemorrhagic risks. The European document is more flexible, advocating for consensus in decision-making. However, it specifies that if intervention precedes surgery, a 4-week waiting period is recommended—a common practice when surgery completes revascularization after primary angioplasty. Additionally, extending DAPT for the first year is suggested for standard ischemic risk scenarios.

The European document, reflecting its cardiological perspective, reviews functional implications of initiating treatment with one approach versus the other. For intermediate lesions, surgery-first strategies reduce lesion significance, providing potential stability until intervention. Conversely, if intervention precedes surgery, formulas used for fractional flow reserve (FFR) calculations increase residual LAD lesion significance, placing the patient at risk until the surgical stage. These considerations, derived from studies like FAME III, align with the timing recommendations discussed earlier for achieving complete revascularization.

Technical Aspects

The European document places limited emphasis on technical aspects, focusing primarily on the hemodynamic implications outlined earlier. It opens the door to diverse surgical approaches, emphasizing that these should stem from team practice and Heart-Team consensus. The American document delves deeper into the technical specifics of MIDCAB, promoting complete dissection of the internal mammary artery through thoracoscopy to avoid first intercostal branch steal—one of the classical technique’s Achilles’ heels. It also briefly mentions robotic-assisted approaches, which are less common, particularly in our setting.

COMMENTARY:

The growing interest in this therapeutic option, previously considered marginal, is striking, especially when viewed as a strategy designed for stable coronary artery disease. Currently, HMR holds a Class IIb recommendation in the revascularization guidelines. It would be imprudent to endorse a strategy without robust evidence, especially as we await results from the Hybrid Coronary Revascularization trial to draw meaningful conclusions or issue stronger recommendations. However, there is a notable push to promote innovation and challenge established practices.

I hesitate to think that the promotion of HMR is a strategy to boost stent implantation by leveraging “our” mammary arteries. In other words, if surgical patients typically receive poor-quality vein grafts yet have lower revascularization needs, these new stents would seemingly perform better when paired with an IMA-LAD anastomosis. Once again, we face a scenario where PCI may not involve sutures but still operates with precision.

REFERENCE:

Thielmann M, Bonaros N, Barbato E, Barili F, Folliguet T, Friedrich G, et al. Hybrid coronary revascularization: position paper of the European Society of Cardiology Working Group on Cardiovascular Surgery and European Association of Percutaneous Cardiovascular Interventions. Eur J Cardiothorac Surg. 2024 Aug 2;66(2):ezae271. doi: 10.1093/ejcts/ezae271.

Willard R, Scheinerman J, Pupovac S, Patel NC. The Current State of Hybrid Coronary Revascularization. Ann Thorac Surg. 2024 Aug;118(2):318-328. doi: 10.1016/j.athoracsur.2024.04.010.