An implanted device that watches for dangerous fast rhythms and delivers a shock if needed to prevent sudden cardiac arrest. Three modalities: transvenous, subcutaneous (S-ICD), and extravascular (EV-ICD). Performed by Ilyas K. Colombowala, MD, FACC, FHRS, board-certified cardiac electrophysiologist serving Northwest Houston and surrounding communities.
A new procedure center at the Texas Medical Center
The Advanced Cardiovascular Institute at the Texas Medical Center, at 6624 Fannin St, Houston, TX 77030, opens in June 2026, our new ambulatory surgery center for cardiac electrophysiology. It will perform catheter ablation, pacemaker, ICD, and loop recorder procedures in the Texas Medical Center for the comfort and convenience of our patients.
Consultations and follow-up continue at our Hargrave Rd clinic in Northwest Houston, with procedures performed at the most appropriate location: Houston Methodist Willowbrook, Houston Methodist Cypress, Baylor St. Luke’s Medical Center, St. Luke’s The Vintage, Memorial Hermann Memorial City, or the new TMC ASC. Learn more → or call (832) 478-5067 to schedule.
Who needs an ICD
ICDs are recommended for patients at high risk of sudden cardiac death from a ventricular arrhythmia. Two broad indications: primary prevention in patients with reduced heart function (typically EF ≤ 35%) or specific inherited arrhythmia syndromes, and secondary prevention in patients who have survived a cardiac arrest or sustained ventricular tachycardia.
Three modalities: and how we choose
Transvenous ICD. The traditional system, generator under the skin near the collarbone, lead through a vein into the heart. Provides both pacing and defibrillation. The right fit for most patients, particularly those who also need bradycardia pacing or CRT.
Subcutaneous ICD (S-ICD). Generator at the left mid-axillary line, lead tunneled under the skin to the left parasternal area, nothing in the vasculature. Best for younger patients with inherited arrhythmia syndromes, dialysis patients, prior endocarditis, or anyone who needs defibrillation without bradycardia pacing.
Extravascular ICD (EV-ICD). The newest modality, generator at the left mid-axillary line, lead positioned behind the sternum (substernal). Adds anti-tachycardia pacing capability that the S-ICD lacks, while still keeping the lead outside the vasculature.
We discuss which modality is the right fit at the consultation, based on your specific clinical picture, pacing needs, anatomy, and lifestyle.
Living with an ICD
Modern ICDs are smaller, MRI-conditional, and supported by wireless home monitoring that transmits to our office daily. Most patients return to their normal activities within a few weeks. We discuss what a shock feels like, what to do if you get one, driving restrictions specific to your situation, and the emotional side of living with the device, openly, before implantation.
An ICD is recommended for patients at high risk of sudden cardiac death from a dangerous fast rhythm. This includes primary prevention in patients with weakened heart function (usually an ejection fraction of 35 percent or less) or certain inherited arrhythmia syndromes, and secondary prevention in patients who have survived a cardiac arrest or sustained ventricular tachycardia.
What is the difference between the three types of ICD?
A transvenous ICD places a lead through a vein into the heart and provides both pacing and defibrillation, which fits most patients. A subcutaneous ICD (S-ICD) keeps everything outside the blood vessels and suits younger patients, dialysis patients, or those with inherited syndromes who do not need pacing. An extravascular ICD (EV-ICD) also keeps the lead outside the vasculature, behind the breastbone, while adding the anti-tachycardia pacing the S-ICD lacks.
What does an ICD shock feel like?
Patients often describe a shock as a sudden, hard thump or kick in the chest that is over in an instant. It can be startling but means the device is doing its job. Dr. Colombowala discusses what a shock feels like, what to do if you receive one, and the emotional side of living with the device before implantation.
Can I get an MRI with an ICD?
Most modern ICDs are MRI-conditional, which means you can have an MRI under specific conditions and settings. The device is checked and reprogrammed for the scan and restored afterward. Always tell the imaging team you have an ICD so they can follow the correct protocol.
Can I drive with an ICD?
Driving restrictions depend on why you received the ICD and whether you have had a shock, and they differ for personal versus commercial driving. Patients implanted for primary prevention usually have shorter restrictions than those who have had a cardiac arrest. Dr. Colombowala reviews the guidance specific to your situation.
