Is a baseline electrocardiogram (ECG) required before initiating the new medication?

EKG Before Starting Medication

You need a baseline EKG before starting this medication if the patient has cardiac risk factors or if the medication is known to prolong the QT interval. 1

Risk-Stratified Approach

Not all patients require a baseline EKG. The decision depends on two key factors: patient-specific cardiac risk and the medication's cardiac toxicity profile. 1

When a Baseline EKG is Required

Obtain a baseline EKG if the patient has any of the following cardiac risk factors: 2

• Known cardiovascular disease (coronary artery disease, heart failure, structural heart disease, congenital heart disease, arrhythmias, conduction disturbances) 2, 1
• Cardiac symptoms including syncope, near-syncope, chest pain, dyspnea, palpitations 2, 1
• Family history of sudden cardiac death or inherited arrhythmia syndromes (long QT syndrome, Brugada syndrome) 1
• Age >50 years, as this population has 10-fold higher sudden cardiac death rates 1

Always obtain a baseline EKG when prescribing medications with known QT-prolonging effects (Class B/B drugs):* 2, 1

• Tricyclic antidepressants 1
• Phenothiazines (e.g., thioridazine) 1
• Thioxanthenes (e.g., zuclopenthixol) 3
• Certain antipsychotics (particularly high-risk agents) 2, 1
• Methadone (especially when daily dose exceeds 100-120 mg) 1
• Tyrosine kinase inhibitors (sunitinib, sorafenib, vandetanib, crizotinib, nilotinib, lapatinib, dasatinib) 2
• Histone deacetylase inhibitors (vorinostat) 2
• BRAF inhibitors (vemurafenib) 2
• Cyclin-dependent kinase 4/6 inhibitors (ribociclib) 2
• Arsenic trioxide 2
• Macrolides (azithromycin, erythromycin) when used long-term 2

When a Baseline EKG is NOT Required

Patients without cardiac risk factors starting low-risk medications can begin treatment without a baseline EKG. 1 Low-risk agents include most SSRIs, SNRIs, and benzodiazepines, which have minimal pro-arrhythmic potential. 1

Additional Pre-Treatment Considerations

Before prescribing QT-prolonging medications, correct any electrolyte abnormalities: 2

• Hypokalemia and hypomagnesemia must be corrected prior to starting treatment, as these significantly increase the risk of torsades de pointes 2
• Check baseline liver function tests for medications metabolized hepatically (e.g., macrolides) 2

Identify drug-drug interactions that may additively prolong the QT interval, including domperidone, ondansetron, palosetron, granisetron, prochlorperazine, olanzapine, escitalopram, venlafaxine, sertraline, and mirtazapine. 2

Follow-Up EKG Monitoring

For patients on QT-prolonging medications, repeat the EKG: 2, 1

• Within 1-2 weeks after starting medication (ideally at 7 days or when steady-state levels are achieved) 2, 1
• After any significant dose increase 1
• With initiation of new medications that may prolong the QT interval 2
• With development of electrolyte imbalances 2

For long-acting depot antipsychotics (e.g., zuclopenthixol decanoate), obtain a follow-up EKG between the first and second dose (around day 7-10 of the 14-day interval) to detect early QT prolongation before steady-state is achieved. 3

QTc Interpretation and Management

Use the Fridericia formula (QT/RR^1/3) for QTc calculation, as it provides less over- and under-correction in patients with tachycardia or bradycardia. 2

QTc thresholds for action: 2

• QTc >450 ms for men or >470 ms for women at baseline is a contraindication to initiating macrolide or other QT-prolonging therapy 2
• QTc >500 ms or >60 ms increase from baseline warrants stopping the medication 2
• QTc 481-500 ms represents grade 2 prolongation and requires close monitoring 2

Common Pitfalls to Avoid

Do not skip baseline EKG in elderly patients (>50 years), even for "low-risk" medications, as this population has substantially higher sudden cardiac death rates. 1

Do not assume all antipsychotics carry equal risk—they vary significantly in QT-prolonging effects. 1

Do not rely solely on clinical symptoms to detect cardiac abnormalities, as ECG changes often precede symptomatic arrhythmias. 3

Failing to obtain an ECG between doses of long-acting medications can lead to undetected cardiac complications that manifest after multiple injections when steady-state is reached. 3

Evidence Quality

The most comprehensive risk-stratified approach comes from European Heart Journal guidelines, which emphasize that psychiatric patients have higher baseline cardiovascular disease prevalence due to lifestyle factors, poor treatment compliance, and possible shared genetic factors. 1 The ACC/AHA guidelines classify EKG monitoring for medications that may produce adverse effects detectable by ECG changes as a Class I indication, supporting selective rather than universal screening. 1