Can the patient's current medications, including Dapagliflozin (Forxiga), Telmisartan, and Metformin, or comorbidities induce arrhythmias, especially under moderate stress or effort, in the presence of Left Bundle Branch Block (LBBB)?

Medications and Comorbidities That May Induce Arrhythmias in Patients with LBBB Under Moderate Stress

In patients with sinus rhythm and left bundle branch block (LBBB), the current medications (Dapagliflozin, Telmisartan, and Metformin) do not significantly increase the risk of arrhythmias under moderate stress or effort, but careful monitoring is warranted due to the underlying conduction abnormality.

LBBB: Clinical Significance and Risk Assessment

• LBBB itself represents a conduction abnormality that requires thorough evaluation as it may be a marker for underlying structural heart disease 1, 2
• Newly detected LBBB requires transthoracic echocardiography to exclude structural heart disease, which is a standard recommendation 1, 2
• LBBB increases the likelihood of left ventricular systolic dysfunction being diagnosed by echocardiogram 1
• If echocardiogram is unrevealing but structural heart disease is still suspected, advanced imaging (cardiac MRI, CT, or nuclear studies) is reasonable 1, 2

Medication Effects on Arrhythmia Risk in LBBB

Dapagliflozin (SGLT2 inhibitor)

• Dapagliflozin has been shown to actually reduce the risk of atrial fibrillation/flutter events by 19% in patients with type 2 diabetes mellitus 3
• This protective effect is consistent regardless of presence or absence of history of atrial fibrillation, atherosclerotic cardiovascular disease, or heart failure 3
• In heart failure patients with reduced ejection fraction (HFrEF), dapagliflozin demonstrated consistent benefits in reducing worsening heart failure events and cardiovascular death in patients with and without atrial fibrillation 4
• Dapagliflozin appears to be safe and effective across the spectrum of left ventricular ejection fraction, including in patients with severe heart failure 5

Telmisartan and Metformin

• Neither Telmisartan (an ARB) nor Metformin has been specifically associated with increased arrhythmia risk in patients with LBBB 1
• Intraoperative bradycardia is most commonly attributable to sinus node dysfunction and only rarely to worsening atrioventricular conduction 1
• Concomitant drugs such as beta blockers or drugs that block the renin-angiotensin system (like Telmisartan) have been identified as risk factors for intraoperative bradycardia and hypotension, but not specifically for arrhythmias under moderate stress 1

Comorbidities and Arrhythmia Risk in LBBB

• Severe structural or coronary artery disease (heart failure, low LVEF, previous myocardial infarction) represents a high-risk criterion for arrhythmias 1
• The presence of LBBB in patients with heart failure is a criterion for consideration of cardiac resynchronization therapy (CRT), particularly with QRS ≥150 ms 1
• Patients with LBBB should be considered at higher short-term risk requiring prompt evaluation when presenting with heart failure symptoms 2
• Exercise-induced LBBB is associated with increased risk of death and cardiac events 2

Monitoring and Management Recommendations

• Ambulatory electrocardiographic monitoring is useful in patients with symptoms suggestive of intermittent bradycardia with conduction system disease 1
• For patients with LBBB who develop symptoms under moderate stress or effort, consider:
  • Ambulatory ECG monitoring during exercise to document potential arrhythmias 1
  • Stress testing with imaging if ischemic heart disease is suspected 1
  • Electrophysiologic study if symptoms suggest intermittent bradycardia with no demonstrated atrioventricular block 1
• Permanent pacing is not indicated in asymptomatic patients with isolated conduction disease and 1:1 atrioventricular conduction 2

Special Considerations

• The presence of LBBB may mask major abnormalities of ventricular repolarization induced by certain drugs 6
• Many medications can cause or exacerbate arrhythmias, including QT-prolonging drugs that can provoke torsades de pointes, but the current medications (Dapagliflozin, Telmisartan, and Metformin) are not prominently associated with such effects 7
• Complete heart block can occur in the setting of pulmonary artery catheter placement in a patient with underlying LBBB, but the incidence is low 1