Diagnosis and outcome in a prehospital cohort of patients with bundle branch block and suspected acute myocardial infarction

Abstract

Background: Immediate revascularization is beneficial in patients with presumed new-onset bundle branch block myocardial infarction (BBBMI). In the prehospital setting, it is a challenge to diagnose new-onset BBBMI and triage accordingly. Methods: ECG, final diagnosis, and mortality were assessed in a prehospital cohort of 4905 consecutive patients with suspected acute myocardial infarction (AMI). Bundle branch block (BBB) was defined as QRS duration ≥120 ms caused by delayed intraventricular conduction. Mortality and angiography data were obtained from the Central Office of Civil Registration and the Western Denmark Heart Registry. Definite diagnosis of AMI and the onset of BBB were determined by expert consensus. Patients were divided into four groups: with or without AMI and with or without BBB. Mortality was evaluated by Kaplan-Meier plots and compared using log-rank statistics. Results: AMI was diagnosed in 954 patients, of whom 118 had BBB. In 3951 patients without AMI, 436 had BBB. Patients with BBBMI were less often revascularized than patients with AMI without BBB (24 vs. 54%, p<0.001). BBBMI was categorized as new onset in 43 patients of whom two were triaged for acute angioplasty. One-year mortality was 47.2, 17.5, 20.8, and 8.6% (log-rank <0.001) in patients with BBBMI, patients with AMI without BBB, patients with BBB without AMI, and patients without AMI or BBB, respectively. Conclusions: Patients with BBBMI have a high mortality. Less than 25% undergo revascularization and only very few patients with new-onset BBBMI are transferred for urgent revascularization. Focus on improving triage and prehospital identification of high-risk patients with BBB and chest pain could improve outcome.

Prehospital diagnosis of patients with acute myocardial infarction

“…However, some present with ECG changes where acute ischemia is difficult to diagnose. In patients with a suspected AMI, 10% present with bundle branch block (BBB), and patients with BBB and AMI have a significantly higher mortality [30,31]. Patients with presumed newly developed left bundle branch block (LBBB) in relation to AMI are at particular high risk and should be treated as STEMI.…”

“…Patients with presumed newly developed left bundle branch block (LBBB) in relation to AMI are at particular high risk and should be treated as STEMI. It is well established that newly developed right bundle branch block (RBBB) in the setting of AMI, is associated with a similar high mortality, suggesting that acute invasive treatment should also apply in this case [31,32]. The difficulty in identifying ischemia in the ECG in the presence of BBB, results in only a minority of patients with LBBB myocardial infarction being treated with reperfusion therapy as recommended by the guidelines [31,33].…”

“…It is well established that newly developed right bundle branch block (RBBB) in the setting of AMI, is associated with a similar high mortality, suggesting that acute invasive treatment should also apply in this case [31,32]. The difficulty in identifying ischemia in the ECG in the presence of BBB, results in only a minority of patients with LBBB myocardial infarction being treated with reperfusion therapy as recommended by the guidelines [31,33]. The Figure 4: Dependency of distance on the predicted system delay (time from alarm call to primary percutaneous intervention) and the various components of the system delay, in patients with ST-segment elevation myocardial infarction.…”

Outcome of early coronary intervention for acute ST elevation myocardial infarction in a tertiary care cardiac centre in Sri Lanka

“…STEMI was diagnosed when there was chest pain and ST elevation in two consecutive leads or new onset LBB (left bundle branch block) in the electrocardiogram (ECG) [13]. ST elevation in ECG was diagnosed when there was ST elevation at the J point in at least two contiguous leads of ≥ 2 mm (0.2 mV) in men or 1.5 mm (0.15 mV) in women in leads V2-V3 or 1 mm (0.1 mV) in other contiguous chest leads or the limb leads [14]. Rescue PCI was carried out after failed thrombolysis in patients who had poor (<50%) ST resolution in 90 minutes, persistent chest pain or cardiogenic shock.…”

A comparison of rescue and primary percutaneous coronary interventions for acute ST elevation myocardial infarction

“…A diagnosis of STEMI was reached when patients presented with chest pain and ST elevation in two consecutive leads or with new onset LBBB (Left Bundle Branch Block) in electrocardiogram (ECG) 14 . We have taken ST elevation in ECG as ST elevation at the J point in at least 2 contiguous leads of ≥2 mm (0.2 mV) in men or ≥1.5 mm (0.15 mV) in women in leads V2–V3 and/or of ≥1 mm (0.1 mV) in other contiguous chest leads or the limb leads 15 . The diagnosis of acute STEMI was made either at the NHSL or the peripheral hospitals where patients were transferred from.…”