{'fraction_non_alphanumeric': 0.019013360739979446, 'fraction_numerical': 0.0051387461459403904, 'mean_word_length': 6.054347826086956, 'pattern_counts': {'":': 0, '<': 0, '<?xml version=': 0, '>': 0, 'https://': 0, 'lorem ipsum': 0, 'www.': 0, 'xml': 0}, 'pii_count': 0, 'substrings_counts': 0, 'word_list_counts': {'cursed_substrings.json': 0, 'profanity_word_list.json': 0, 'sexual_word_list.json': 0, 'zh_pornsignals.json': 0}}
Variability of electrocardiographic precordial lead placement: a method to improve accuracy and reliability.

Variability in precordial lead placement is a recognized source of electrocardiographic inaccuracy and lack of reproducibility. In an attempt to reduce error, we evaluated a new device to facilitate and guide precordial lead placement. This study involved three phases: (1) comparison of device-guided electrocardiogram with ECGs obtained by deliberate misplacement of precordial leads on the same patient; (2) electrocardiograms obtained by using the precordial lead device versus those obtained by standard technician methods; (3) reproducibility of precordial electrocardiographic leads between two technicians using the device to guide lead placement. Deliberate misplacement of precordial leads by 2 cm resulted in significant electrocardiographic interpretation changes in all patients. Comparing electrocardiograms obtained after device-guided precordial placement with those obtained after technician placement resulted in variations in 60% of patients including changes in R-wave amplitude, ST segments, Q waves, and transition zone. Significant Q-wave appearance/disappearance and/or significant ST-segment elevation/depression occurred in 19% of patients in Phase II. Sixteen percent of electrocardiograms showed significant changes when analyzed by an experienced electrocardiographer and 10% when interpreted by computer. Variable lead placements and resulting electrocardiographic alterations were not seen by either of two technicians when the device was used. This study confirms the widespread variability in precordial electrocardiograms secondary to lead misplacement. The use of a device to assist in the placement of precordial leads ensures accuracy and reproducibility of electrocardiography. Improved precision and quality control in this laboratory test have important implications in health care and its costs.