From the Guidelines
Scarbossa criteria are not applicable to atrial paced rhythms. These criteria were specifically developed to diagnose acute myocardial infarction in the presence of left bundle branch block (LBBB), not for paced rhythms. When a patient has an atrial paced rhythm, the ventricular activation sequence is still primarily through the normal conduction system, which means the QRS morphology is usually normal or near-normal unless there is underlying conduction disease. For evaluating myocardial infarction in patients with atrial pacing, standard ECG criteria for STEMI can generally be applied since the ventricular depolarization pattern is not significantly altered by atrial pacing alone. However, if the patient has ventricular pacing or develops aberrant conduction during atrial pacing, then modified criteria such as the Sgarbossa criteria adaptations for ventricular paced rhythms would be more appropriate, as seen in the study by Sgarbossa et al 1. The fundamental reason Sgarbossa criteria don't apply to atrial pacing is that they were designed to identify ST-segment changes that are discordant with the abnormal QRS complexes seen in LBBB, which is not the electrical pattern produced by atrial pacing.
Some key points to consider include:
- The Sgarbossa criteria were developed based on the expected ECG patterns in patients with altered intraventricular conduction, such as LBBB, where the QRS complex-T-wave axes discordance is a key feature 1.
- In patients with LBBB, the loss of this normal QRS complex T-wave axes discordance may imply injury or ischemia, and the Sgarbossa criteria can help identify this 1.
- The study by Sgarbossa et al found that the criteria had a high specificity and positive predictive value for AMI in patients with LBBB, but this does not necessarily apply to patients with atrial paced rhythms 1.
- Theoretical applications of these rules to patients with RBBB, atypical BBB, and ventricular paced patterns have been considered, but only the ventricular paced pattern has been investigated, as reported by Sgarbossa et al 1.
Overall, the Sgarbossa criteria are not directly applicable to atrial paced rhythms, and standard ECG criteria for STEMI should be used instead, unless there is evidence of ventricular pacing or aberrant conduction.
From the Research
Applicability of Sgarbossa Criteria to Atrial Paced Rhythm
The Sgarbossa criteria are a set of electrocardiographic criteria used to diagnose acute myocardial infarction (AMI) in patients with ventricular paced rhythms or left bundle branch blocks. However, the question of whether these criteria can be applied to atrial paced rhythms remains.
Evidence from Studies
- The study by 2 compared the sensitivity of the modified Sgarbossa criteria (MSC) to that of the original Sgarbossa criteria for the diagnosis of occlusion myocardial infarction in patients with ventricular paced rhythm, but did not address atrial paced rhythms.
- A case report by 3 suggested that the Smith-modified Sgarbossa criteria can be applied to diagnose STEMI in patients with paced rhythms, but the sensitivity and specificity of these criteria in paced rhythms are not well documented.
- The study by 4 evaluated the Sgarbossa criteria in ventricular-paced ECGs and found that ST-segment elevation >5mm discordant with the QRS complex was a highly specific criterion for AMI, but again, did not address atrial paced rhythms.
Key Findings
- There is limited evidence on the applicability of Sgarbossa criteria to atrial paced rhythms.
- The available studies focus on ventricular paced rhythms or left bundle branch blocks, and do not provide direct evidence for atrial paced rhythms.
- The Smith-modified Sgarbossa criteria may be applicable to paced rhythms, but more research is needed to confirm this.
Implications
- The diagnosis of AMI in patients with atrial paced rhythms may require alternative approaches, such as the use of cardiac biomarkers or echocardiography, as suggested by 5 and 6.
- Further studies are needed to evaluate the applicability of Sgarbossa criteria to atrial paced rhythms and to develop evidence-based guidelines for the diagnosis of AMI in these patients.