CTI ablation is a minimally invasive, catheter-based procedure used to treat a specific abnormal heart rhythm. It targets the Cavo-Tricuspid Isthmus (CTI), a narrow strip of tissue in the right side of the heart. The procedure delivers energy to this anatomical location to permanently interrupt an electrical short circuit. This intervention is highly effective for restoring a normal heart rhythm without open-heart surgery.
The Heart Rhythm Disorder Requiring Treatment
The condition most commonly treated is typical Atrial Flutter, an arrhythmia caused by a single, large electrical loop in the upper right chamber of the heart. This loop rapidly circles the tricuspid valve, causing the atrium to beat at a fast rate, often over 250 beats per minute. The CTI sustains this rapid, organized electrical activity by acting as the final pathway for the circuit to complete itself.
The CTI is a segment of muscle tissue situated between the tricuspid valve and the opening of the inferior vena cava. In Atrial Flutter, the electrical impulse is forced through this narrow isthmus, making it the most vulnerable point of the circuit. While medications can sometimes slow the heart rate, they are often insufficient for long-term management. Ablation is considered the standard treatment because it physically eliminates the electrical path, offering a permanent solution.
Navigating the CTI Ablation Procedure
The CTI ablation is performed in a specialized electrophysiology laboratory, typically under conscious sedation or general anesthesia. The procedure begins with the insertion of thin, flexible catheters into a major vein, usually the femoral vein in the groin area. These catheters are guided up to the right atrium of the heart using X-ray imaging for navigation.
Once inside the heart, the catheters perform an electrophysiology study, mapping the electrical activity to confirm the flutter circuit location and the CTI boundaries. Specialized three-dimensional mapping systems, such as CARTO or EnSite, are often used to create a detailed, real-time computer model of the right atrium. This reduces dependence on X-ray exposure and allows the physician to pinpoint the CTI. The physician then visually guides the ablation catheter to the target tissue.
The core of the procedure involves delivering energy, most commonly radiofrequency energy, through the ablation catheter tip to the CTI tissue. Radiofrequency energy generates heat, creating a controlled burn that scars the tissue along a continuous line. This scar tissue line must stretch from the tricuspid valve annulus to the inferior vena cava opening, creating a complete barrier. This permanent lesion blocks the electrical pathway, stopping the reentrant circuit that causes the flutter.
In some cases, cryoablation, which uses extreme cold, may be used instead of heat to destroy the tissue. Regardless of the energy source, the procedural endpoint is achieving “bidirectional conduction block.” This means electrical signals can no longer pass through the CTI in either direction. The physician confirms this block using specific pacing maneuvers and electrical measurements before concluding the ablation. The goal is to ensure the lesion is transmural, extending through the full thickness of the heart muscle to prevent the circuit from reconnecting.
Preparing for the Intervention and the Recovery Process
Preparation for CTI ablation begins several days prior, focusing on medication management and fasting. Antiarrhythmic medications are often discontinued five half-lives before the procedure to ensure the heart rhythm is vulnerable to mapping. Patients taking blood thinners (anticoagulants) receive specific instructions, which may involve temporarily stopping the medication 48 hours before or continuing it without interruption.
Patients are instructed not to eat or drink anything after midnight on the day of the procedure. Necessary pre-procedure tests, such as blood work and an echocardiogram, are completed to assess the patient’s overall health and heart structure. This ensures the environment is safe and optimal for the electrical mapping and ablation.
Following the ablation, the catheters and sheaths are removed from the groin access site. Pressure is immediately applied to the puncture site to prevent bleeding, often followed by a device that maintains pressure for a few hours. The patient is required to lie flat in bed for several hours afterward to ensure the puncture site heals properly and minimize the risk of bruising or bleeding.
Most patients spend a night in the hospital for observation, where their heart rhythm is continuously monitored. They may experience mild soreness or bruising at the groin site, which is common and temporary. Instructions for resuming normal activities, including showering, lifting, and exercise, are provided before discharge, with routine activities cleared within a few days.
Expected Success Rates and Potential Complications
CTI ablation is one of the most effective catheter ablation procedures available, with acute success rates for achieving the electrical block typically reported above 90%. The long-term recurrence rate for typical Atrial Flutter after a successful procedure is low, often falling below 10%. The effectiveness is closely tied to achieving a complete and durable bidirectional block across the isthmus.
While the procedure has a high success profile, potential complications exist, though the overall acute complication rate is low, generally around 2.6%. The most common issue is localized bleeding, bruising, or swelling at the femoral vein access site. Rare complications include the risk of a blood clot forming or a vascular injury. Rarely, the procedure can lead to a perforation of the heart wall or damage to structures like the atrioventricular node, potentially requiring a permanent pacemaker. Many patients who experience Atrial Flutter also have a predisposition to Atrial Fibrillation (AF), and a portion may experience new-onset or recurrent AF in the future.