From the Guidelines
Prolonged QTc remains relevant even with a pacemaker (PPM) in place. While a pacemaker can regulate heart rate and prevent bradycardia-related QT prolongation, it does not directly correct the underlying repolarization abnormality that causes QT prolongation. According to the HRS/ACCF expert consensus statement on pacemaker device and mode selection 1, dual-chamber or atrial pacing is recommended for symptomatic or high-risk patients with congenital long QT syndrome.
Key Considerations
- Patients with pacemakers should still be monitored for QT prolongation, especially when taking QT-prolonging medications such as certain antiarrhythmics (amiodarone, sotalol), antipsychotics (haloperidol, quetiapine), antibiotics (macrolides, fluoroquinolones), or antidepressants (citalopram, escitalopram) 1.
- The risk of torsades de pointes and other ventricular arrhythmias persists despite pacemaker presence because these arrhythmias result from abnormal ventricular repolarization, which the pacemaker does not correct.
- Regular ECG monitoring is recommended for patients with pacemakers who have known QT prolongation or who are taking QT-prolonging medications.
- Electrolyte imbalances (particularly hypokalemia, hypomagnesemia, and hypocalcemia) should be corrected promptly as they can exacerbate QT prolongation even in paced rhythms 1.
Management of QT Prolongation
- The first step in managing QT prolongation is to stop medications known to prolong the QT interval 1.
- Correct electrolyte imbalance and other acute precipitants (eg, drug overdose or poisoning) 1.
- Magnesium is commonly used to treat torsades de pointes VT (polymorphic VT associated with long QT interval), although its effectiveness is supported by only observational studies 1.
From the Research
Prolonged QTc Interval and Pacemaker Dependency
- The relationship between prolonged QTc interval and pacemaker dependency is complex, with some studies suggesting that QTc prolongation in pacemaker-dependent patients may not represent a true repolarization abnormality 2.
- A study found that QTc prolongation in ventricular pacemaker patients is not associated with an increased risk of fatal arrhythmia, and these patients can safely receive medications with known potential to prolong ventricular repolarization 2.
- However, another study noted that while pacemakers can offer partial protection against torsades de pointes (TdP) by preventing bradycardia, they are not a guarantee against TdP, and patients with pacemakers should still be monitored for QTc prolongation 3.
Risk Factors for QTc Prolongation
- Several risk factors have been identified for QTc prolongation, including hypokalemia, use of diuretics, antiarrhythmic drugs, and QTc-prolonging drugs 4.
- A systematic review found very strong evidence for the association between hypokalemia, use of diuretics, antiarrhythmic drugs, and QTc-prolonging drugs and QTc prolongation 4.
- Other factors, such as hyperlipidemia, use of digoxin or statins, neurological disorders, diabetes, renal failure, depression, alcohol abuse, heart rate, pulmonary disorders, hormone replacement therapy, hypomagnesemia, history of a prolonged QTc interval/TdP, familial history of cardiovascular disease, and use of only QTc-prolonging drugs of list 2 or 3 of CredibleMeds, were found to have little or no evidence for association with QTc prolongation 4.
Pacemaker Settings and QTc Prolongation
- A study found that programmed lower rates < or = 70 beats/min are not protective against TdP, and that TdP can occur even with a functional permanent pacemaker 5.
- The study suggested that rate smoothing algorithms may be able to prevent TdP when the baseline rate is programmed < or = 70 beats/min, but further research is needed to confirm this 5.
- Another study recommended that patients with pacemakers should be educated to go directly to the emergency room if they experience palpitations, lightheadedness, dizziness, or syncope, and that close monitoring for QTc prolongation is necessary to prevent TdP 6.