Applying Shocks in Eccentric v Concentric Rocks
Q&A with Dr. Ziad Ali about the Disrupt CAD Pooled OCT Eccentric vs Concentric Analysis at TCT21
Following its presentation at TCT21 in a moderated poster session, we caught up with Ziad Ali, M.D., DPhil, Director of the DeMatteis Cardiovascular Institute and Investigational Interventional Cardiology at St Francis Hospital & Heart Center, to get his thoughts on the implications of the concentric vs eccentric calcium analysis among those patients enrolled in the Disrupt CAD clinical program.
Why is eccentric calcium so challenging to modify?
Dr. Ali: Simple. It's hard to modify. Balloon based modification leads to the creation of a dissection at the site of minimal resistance. That is the fibro-calcific interface, the place where the fibrous tissue meets the calcium. This dissection allows vessel expansion, but the calcium remains unmodified. After stenting the calcium protrudes back into towards the lumen, reducing the potential MSA. With atherectomy, the wire and thus burr must be biased into the calcium. If it is not, there is no chance of lesion modification. With IVL, most of the energy is lost into the soft tissue. So if there is only 90 degrees of calcification, i.e 25% of the vessel circumference, 75% of the energy is dissipated. More specifically, the maximum energy in IVL is immediately perpendicular to the electrode.
Why is the DISRUPT CAD OCT Pooled analysis important for current clinical practice?
Dr. Ali: Simple. There is power in numbers. These data show categorically that the predominant mechanism of IVL is calcium fracture, and that the more the calcium the greater the fracture. The ability of IVL to create luminal gain in severe calcification is unquestionable. Overall the mean stent expansion and stent expansion at the site of max calcium was greater than 100%. The fact that the minimal lumen area was never at the site of maximum calcification is proof in and of itself.
What were the findings in the OCT analysis in concentric and eccentric lesions? How do you explain these results?
Dr. Ali: Fractures are much less common in eccentric rather than concentric lesions. But that’s ok, because you need less fractures in eccentric calcium because the rest of the artery is conformable. In general, lesion modification for an eccentric calcified lesion is unnecessary, unless it’s a calcified nodule. That being said, within a heavily calcified segment of vessel, there will be multiple morphologies along the length of that lesion. Some concentric, some eccentric. IVL helps all the way along the length by creating lots of fractures at the more concentric sites and less fractures, because less are needed, at the eccentric sites. The take home message is that even in eccentric lesions there was a consistent improvement in stent expansion and luminal gain compared to concentric lesions. So IVL liberates vascular compliance through calcium fracture appropriate to need.
From your perspective, how do these outcomes compare to what you see in the clinic?
Dr. Ali: We are definitely still learning, but the clinical experience is very similar to the trial results. Not surprising, there was tremendous consistency in terms of safety and efficacy among all of Disrupt CAD studies so we wouldn’t expect that different in the real world. At St Francis we have done over 100 commercial cases and one of our more noticeable findings is how well tolerated IVL is in the very high-risk patient. Very low EF, high EDP, severe PAH, multivessel disease. We don’t see the same hemodynamic fluctuations we see sometimes with other lesion prep strategies.
Are there any coronary IVL best practices that will help interventionalists achieve similar results to what was reported?
Dr. Ali: Image image image. Intravascular imaging determines the severity and distribution of calcium. Using the St Francis Calcium Scores can help determine whether or not you even need advanced lesion prep. By OCT, if the calcium is 5mm long, 0.5mm thick and 50% of the arc, advanced prep is necessary. By IVUS, circumferential, 270 degrees for 5mm, < 3.5mm at the site of calcification and calcified nodule, advanced prep is necessary. Remember the more the rock the better the shock!
Dr. Ali is a paid consultant and equity holder in Shockwave Medical.
Important Safety Information
Please contact your local Shockwave representative for specific country availability and refer to the Shockwave C2 instructions for use containing important safety information.
Indications for Use—The Shockwave Intravascular Lithotripsy (IVL) System with the Shockwave C2 Coronary IVL Catheter is indicated for lithotripsy-enabled, low-pressure balloon dilatation of severely calcified, stenotic de novo coronary arteries prior to stenting.
Contraindications—The Shockwave C2 Coronary IVL System is contraindicated for the following: This device is not intended for stent delivery. This device is not intended for use in carotid or cerebrovascular arteries.
Warnings— Use the IVL Generator in accordance with recommended settings as stated in the Operator’s Manual. The risk of a dissection or perforation is increased in severely calcified lesions undergoing percutaneous treatment, including IVL. Appropriate provisional interventions should be readily available. Balloon loss of pressure was associated with a numerical increase in dissection which was not statistically significant and was not associated with MACE. Analysis indicates calcium length is a predictor of dissection and balloon loss of pressure. IVL generates mechanical pulses which may cause atrial or ventricular capture in bradycardic patients. In patients with implantable pacemakers and defibrillators, the asynchronous capture may interact with the sensing capabilities. Monitoring of the electrocardiographic rhythm and continuous arterial pressure during IVL treatment is required. In the event of clinically significant hemodynamic effects, temporarily cease delivery of IVL therapy.
Precautions— Only to be used by physicians trained in angiography and intravascular coronary procedures. Use only the recommended balloon inflation medium. Hydrophilic coating to be wet only with normal saline or water and care must be taken with sharp objects to avoid damage to the hydrophilic coating. Appropriate anticoagulant therapy should be administered by the physician. Precaution should be taken when treating patients with previous stenting within 5mm of target lesion.
Potential adverse effects consistent with standard based cardiac interventions include– Abrupt vessel closure – Allergic reaction to contrast medium, anticoagulant and/or antithrombotic therapy-Aneurysm-Arrhythmia-Arteriovenous fistula-Bleeding complications-Cardiac tamponade or pericardial effusion-Cardiopulmonary arrest-Cerebrovascular accident (CVA)-Coronary artery/vessel occlusion, perforation, rupture or dissection-Coronary artery spasm-Death-Emboli (air, tissue, thrombus or atherosclerotic emboli)-Emergency or non-emergency coronary artery bypass surgery-Emergency or non-emergency percutaneous coronary intervention-Entry site complications-Fracture of the guide wire or failure/malfunction of any component of the device that may or may not lead to device embolism, dissection, serious injury or surgical intervention-Hematoma at the vascular access site(s)-Hemorrhage-Hypertension/Hypotension-Infection/sepsis/fever-Myocardial Infarction-Myocardial Ischemia or unstable angina-Pain-Peripheral Ischemia-Pseudoaneurysm-Renal failure/insufficiency-Restenosis of the treated coronary artery leading to revascularization-Shock/pulmonary edema-Slow flow, no reflow, or abrupt closure of coronary artery-Stroke-Thrombus-Vessel closure, abrupt-Vessel injury requiring surgical repair-Vessel dissection, perforation, rupture, or spasm.
Risks identified as related to the device and its use: Allergic/immunologic reaction to the catheter material(s) or coating-Device malfunction, failure, or balloon loss of pressure leading to device embolism, dissection, serious injury or surgical intervention-Atrial or ventricular extrasystole-Atrial or ventricular capture.
Prior to use, please reference the Instructions for Use for more information on warnings, precautions and adverse events. https://shockwavemedical.com/IFU