How does LBBB make diagnosing myocardial infarction more difficult?
If a person has LBBB it can make it more difficult to make an infarct diagnosis based on an ECG alone. This is because the baseline ST segments and T waves are often shifted in a discordant direction which can confuse an AMI diagnosis. Usually an infarct diagnosis isn’t made on an ECG alone. If there is doubt, the Sgarbossa criteria (see here http://www.ncbi.nlm.nih.gov/pubmed/85592… ) can be used, although studies show that electrocardiographic criteria are poor predictors of AMI in LBBB situations and suggested that all patients suspected of AMI with LBBB should be considered for thrombolysis regardless. Of course, enzyme studies should always be done. And the william marrow is the mnemonic I use. It’s ‘W’on V1 and ‘M’ + V6 which are specific for LBBB because in V1 it is usually in ‘W’ pattern, while in V6 it tends to be M. Remember, when LBBB is present, the septum depolarizes from R to L, not from
