Terapia de resincronización cardíaca

In some people with heart failure, the electrical signal spreads through the ventricles unevenly — typically because of a left bundle branch block. One wall contracts while the opposite wall is still relaxing, so the chambers work against each other and pump less efficiently than their muscle should allow. This is called dyssynchrony.

Cardiac resynchronization therapy, or CRT, corrects the timing. An additional lead is placed to pace the left ventricle alongside the right, so both walls contract together again. It is often described as biventricular pacing.

Unlike a standard pacemaker, which addresses a rate that is too slow, CRT addresses coordination — and in the right patient it can improve symptoms, exercise tolerance and the heart's pumping function, and reduce hospitalizations.

CRT is offered to a specific group, and the selection criteria matter because the therapy helps most in patients who meet them:

• A reduced ejection fraction, generally 35 percent or below
• A wide QRS on the EKG — particularly a left bundle branch block, and generally 150 milliseconds or wider, where the benefit is greatest
• Ongoing heart failure symptoms despite optimal medication, which is why medical therapy is maximized first
• Selected patients who will require a great deal of ventricular pacing for other reasons

Many candidates also meet criteria for a defibrillator, in which case a combined device (CRT-D) is implanted. A device without defibrillation is a CRT-P. Which is appropriate depends on your risk of dangerous ventricular arrhythmias, and is a decision to make explicitly with your electrophysiologist and heart failure cardiologist.

Implantation resembles a pacemaker but is more involved and usually takes two to four hours, because the left ventricular lead is placed through the coronary sinus — a vein on the outside of the heart — into a branch positioned over the left ventricular wall. Anatomy varies, and finding a stable branch with good pacing and no diaphragm stimulation is the technically demanding part.

Sedation with local anesthetic is typical. Most patients stay overnight, and recovery mirrors a pacemaker: keep the site clean and dry, limit arm movement above the shoulder and avoid heavy lifting for four to six weeks, and report fever, redness, drainage or increasing swelling promptly.

Benefit is not always immediate — improvement in symptoms and in ejection fraction often develops over three to six months. The device is then fine-tuned: pacing timing is adjusted, and the percentage of beats actually being resynchronized is checked. That percentage should be very high, and if it is not — often because of atrial fibrillation or frequent ectopic beats — addressing the cause is what allows the therapy to work.

Not everyone responds, which is discussed honestly beforehand. Continued heart failure medication, remote device monitoring and regular follow-up remain part of care either way.