Can a patient with Left Bundle Branch Block (LBBB) undergo a treadmill nuclear stress test?

From the Guidelines

Treadmill nuclear stress tests are generally not recommended for patients with Left Bundle Branch Block (LBBB) due to the high risk of false-positive results. Instead, a pharmacological nuclear stress test using vasodilators like regadenoson (Lexiscan), dipyridamole (Persantine), or adenosine is the preferred approach, as recommended by the 2014 ACC/AHA guideline on perioperative cardiovascular evaluation and management of patients undergoing noncardiac surgery 1. This recommendation exists because LBBB can cause false-positive results during exercise stress testing due to septal perfusion defects that occur with increased heart rate, even in the absence of coronary artery disease.

The evidence from the 2007 ACC/AHA guidelines on perioperative cardiovascular evaluation and care for noncardiac surgery also supports this approach, stating that pharmacologic stress testing with either perfusion scintigraphy or dobutamine stress echocardiography is preferred over exercise stress testing for the preoperative evaluation of CAD in patients with LBBB 1. Additionally, the 2012 ACCF/AHA/ACP/AATS/PCNA/SCAI/STS guideline for the diagnosis and management of patients with stable ischemic heart disease recommends pharmacological stress with either nuclear MPI or echocardiography for risk assessment in patients with SIHD who have LBBB on ECG, regardless of ability to exercise to an adequate workload 1.

Some key points to consider when performing a pharmacological nuclear stress test in patients with LBBB include:

• The use of vasodilators like regadenoson, dipyridamole, or adenosine, which have a more favorable side-effect profile compared to dobutamine 1
• The administration of the medication intravenously while the patient remains at rest, avoiding the heart rate increase that triggers false positives
• The injection of a nuclear tracer and obtaining images to assess myocardial perfusion
• The potential need for separate exercise capacity assessment, which can be done using a modified, low-level exercise approach with careful monitoring, but is not standard practice and should be determined by a cardiologist familiar with the patient's specific situation.

Overall, the evidence suggests that pharmacological nuclear stress testing is the preferred approach for patients with LBBB, and treadmill nuclear stress tests should be avoided due to the high risk of false-positive results.

From the Research

Treadmill Nuclear Stress Test with LBBB

• The feasibility of performing a treadmill nuclear stress test in patients with Left Bundle Branch Block (LBBB) has been explored in several studies 2, 3, 4.
• A study published in 2013 found that regadenoson, a pharmacologic stress agent, can be used in patients with LBBB, but it may cause false-positive results in the setting of an elevated heart rate 2.
• Another study from 2012 reported on four patients with rate-dependent LBBB who underwent exercise treadmill tests (ETT) and myocardial perfusion SPECT imaging, with no adverse cardiac events noted 3.
• The study suggested that it may be possible to continue ETT in patients with rate-dependent LBBB, but the limited number of patients enrolled did not allow for a definitive conclusion.
• Earlier research from 1979 evaluated the value of treadmill exercise testing in patients with complete bundle branch block, including LBBB, and found that exercise electrocardiography was unreliable in detecting coronary artery disease in patients with complete LBBB due to a high incidence of false-positive results 4.
• More recent studies have focused on the use of regadenoson as a stress agent in various patient populations, including those with LBBB, and have found it to be safe and well-tolerated 5, 6.
• However, the specific issue of performing a treadmill nuclear stress test with LBBB remains a topic of interest, with some studies suggesting that it may be feasible in certain cases, while others highlight the potential for false-positive results.

Key Findings

• Regadenoson can be used as a stress agent in patients with LBBB, but may cause false-positive results 2.
• Exercise treadmill tests can be safely performed in patients with rate-dependent LBBB, but the limited data available do not allow for a definitive conclusion 3.
• Earlier research suggested that exercise electrocardiography is unreliable in detecting coronary artery disease in patients with complete LBBB due to false-positive results 4.
• Regadenoson has been found to be safe and well-tolerated in various patient populations, including those with LBBB 5, 6.