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When arrhythmias complicate the postoperative period

The postoperative period following cardiac surgery (or any other type of surgery) is a particularly delicate time in many respects. The body functions are still not fully restored, organ-function parameters are unstable, and the patients are very vulnerable. In addition, the specific features of each postoperative period are determined by the type of procedure performed and the individual characteristics of the patient. Current approaches to anesthesia are based largely on intravenous drugs (rather than inhalation agents). As a result, the immediate postsurgical period—that is, the initial hours spent in intensive care unit (ICU)—are much easier. The type and duration of anesthesia (which also reflects the duration of surgery) are the main factors that determine when the patient will resume consciousness and when his/her “vital functions” (also referred to as “hemodynamic parameters”) will be fully restored. This means adequate left ventricular pumping, normal heart rate, appropriate blood pressure, effective respiratory activity, and adequate renal function. Acceptable respiratory function, left ventricular pumping, and arterial blood pressure are key elements for ensuring optimal oxygenation of the body tissues. Renal function is also important for normalizing electrolyte levels and restoring the acid-base balance, both of which occur within a few hours after surgery. The most frequent arrhythmias seen in ICUs include sinus tachycardia and bradycardia, ventricular ectopic beats, and atrial fibrillation. In certain cases (fortunately less common), ventricular tachycardia and ventricular fibrillation may also develop. Sometimes, the arrhythmia is caused by the administration of certain drugs. Several types of parenteral drugs that are widely used in ICUs have well known arrhythmogenic effects, including the positive inotropes and vasoconstrictors like dopamine and epinephrine. Patients who are regaining consciousness are closely monitored by the ICU staff, clinically and with laboratory tests, to ensure that full function is restored to each vital organ and to detect alterations (such as hypothermia, acidosis, hypovolemia, hypoxemia, etc.) that can negatively affect the vital functions and increase the risk of cardiac arrhythmias or conduction disturbances. As time passes, the numerous factors capable of triggering cardiac rhythm disturbances (only a few of which were mentioned above) weaken considerably, and there is a significant decrease in the frequency of arrhythmias. Arrhythmias can still occur after the patient is transferred to a noncritical care area. Most are triggered by fever, pericarditis, anemia, and electrolyte disturbances. Tachycardia is common during this post-ICU phase, and there may be episodes of atrial fibrillation, some followed by spontaneous return to a sinus rhythm. The frequency of rhythm disturbances decreases progressively with time, and these events are decidedly rare when patients are in the rehabilitation department or after they have returned home. The arrhythmias seen in this phase (2-3 weeks after surgery) are relatively inconsequential, such as atrial or ventricular ectopic beats or atrial fibrillation and / or atrial flutter. In a non-negligible number of cases, the electrical activity of the heart may be disturbed by drugs used in maintenance therapy. Vasodilators (nifedipine) can cause tachycardia, beta blockers (metoprolol) and calcium-channel blockers (verapamil) may be responsible for bradycardia, and so on. In these cases, adjusting the drug therapy usually eliminates the rhythm and rate anomalies. The most common postoperative arrhythmia is without a doubt atrial fibrillation (AF), which occurs in 20% – 40% of patients who undergo open-heart surgery. The incidence  is higher in older patients, those who have had valve surgery (as opposed to coronary artery procedures), individuals with a preoperative history of atrial arrhythmias, and those with chronic pulmonary disease or obstructive peripheral arterial disease. Incidence peaks during the first few days after surgery, but the arrhythmia can also occur weeks after the operation (Fig. 1).

ECG A ok

ECG B ok

ECG C ok

Figure 1. EKG strips recorded in an 80-year-old woman with severe calcific aortic valve stenosis associated with moderate (NYHA class III) dyspnea on exertion. A) On admission for aortic valve replacement. B) On the second postoperative day, when she went from a normal sinus rhythm to atrial fibrillation. C) On the fourth postoperative day, when sinus rhythm was spontaneously restored.

In patients with long-standing permanent atrial fibrillation before surgery, the AF is very likely to persist even after the operation. This is particularly true when the arrhythmia is associated with major enlargement of the left atrium. Surgical correction of a dysfunctional valve is not enough to restore sinus rhythm. In some cases, however, the surgeon can perform an additional procedure known as the Maze procedure, which may control the arrhythmia. A series of incisions are made in the wall of the left atrium to interrupt the conduction of anomalous impulses. The effect is similar to that achieved with circumferential pulmonary vein ablation (CPVA), a procedure performed in the electrophysiology lab with radiofrequency catheters, which destroy the arrhythmogenic tissue by thermal coagulation. It involves the “disconnection” of all pulmonary veins with large, point-by-point circumferential lesions (see Treatments / Atrial Fibrillation Ablation on our site).

Drugs can also be used to prevent the occurrence of postoperative AF (AF prophylaxis). Most studies on this approach have focused on the use of beta-blockers or amiodarone (intravenous or oral) for preventing new-onset postoperative atrial fibrillation. As with other forms of AF, the aims of treatment are to control the ventricular rate with drugs that block AV node conduction, to reduce the risk of thrombosis with anticoagulation, and to restore sinus rhythm. The time-frame and methods will depend on the clinical and hemodynamic status of the patient. Fortunately, in many cases sinus rhythm is restored spontaneously within a matter of hours or days. In other cases, pharmacological or electrical cardioversion is required. Oral antiarrhythmic drugs are then administered for several weeks to prevent recurrence of the arrhythmia.

Postoperative atrial fibrillation is naturally associated with longer hospital stays and higher costs.

Vladimir Guluta, MD

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