Interatrial block: Pandemic prevalence concealed by anachronistic electrocardiographic standards

Abstract

SummaryBackground: Interatrial block (IAB; P waves ≥ 110 ms duration) has been reported in over 40% of unselected patients in sinus rhythm at widely separated general hospitals. It is thus of "pandemic" proportions. It should be better appreciated because it represents a large, baggy, poorly functional left atrium and is a forerunner of atrial fibrillation, atrial flutter, and other arrhythmias.Hypothesis: A search of all 12 leads will disclose the true prevalence of IAB in contrast to traditional reliance on lead II, as widely proposed in textbooks and other literature.Methods: In all, 500 consecutive unselected electrocardiograms (ECGs) were investigated using every lead and a magnifying graticule. For greater specificity, a minimal P duration of ≥ 120 ms was selected.Results: Thirty-one ECGs were discarded because of atrial arrhythmia, poor baseline, or undetectable P waves, leaving a base of 469 ECGs, the denominator for the results. A total of 182 patients had IAB, representing 38.8% of this series. The widest P wave was usually found in multiple leads (95.1% of patients). The widest P waves were found only in precordial leads in 59 patients and only in limb leads in 18 patients. "Traditional" lead II detected only 97 cases (53.3%), and IAB was found more frequently in leads V 3 and V4.Conclusions: Results confirm the pandemic frequency of IAB in one-third of hospitalized patients. Interpreters of ECGs should seek IAB in all 12 leads since reliance on lead II alone resulted in only 53.3% of the total cases. Its prevalence and serious implications with regard to patients' current and future status make this necessary.

Prospective evaluation of atrial tachyarrhythmias in patients with interatrial block

“…ECGs had been recorded from a Marquette 2000 electrocardiograph (Marquette Electronics Incorporated, Milwaukee, WI) at 25 mm/s with 10 mm/mV standardization. ECGs were evaluated for interatrial block using the greatest duration of P-waves in every appropriate lead as measured with a magnifying graticule (reproducibility and interobserver concordance N 95%) [10]. To increase specificity and because 1 mm represents 40 ms on ECGs with such standardization, 120 ms (which is also the mode P-wave duration in interatrial block) was used as our diagnostic criterion for interatrial block [10].…”

“…ECGs were evaluated for interatrial block using the greatest duration of P-waves in every appropriate lead as measured with a magnifying graticule (reproducibility and interobserver concordance N 95%) [10]. To increase specificity and because 1 mm represents 40 ms on ECGs with such standardization, 120 ms (which is also the mode P-wave duration in interatrial block) was used as our diagnostic criterion for interatrial block [10]. The onset of the P-wave was defined as the junction between the isoelectric T-P baseline and the beginning of the P deflection, while the end of the P-wave as the junction between the terminal point of the P deflection and the PR segment.…”

“…Besides, P-wave durations measured in this manner may rarely correlate precisely with the actual total atrial activation time recorded during electrophysiologic evaluations. However, altering the sweep speed or gain of the ECG in an attempt to achieve optimal results for diagnosis of interatrial block could be impractical at the bedside, where the essence of this cheap, quick and efficient clinical tool is most desired [10].…”

Bayés’ syndrome: the association between interatrial block and supraventricular arrhythmias

“…In one study with Jairath et al and Frisella et al, 41% of patients were found to have IAB. In another with Asad et al, in which 1000 consecutive ECGs were analyzed, 43% were found to have IAB [21][22][23].…”

Interatrial Block: The Pandemic Remains Poorly Perceived

“…Conduction delay— block by electrocardiogram (ECG)—is evident as excessive time of inscription of any wave or interval. IAB—abnormally delayed activation passing from the right to the left atrium—is extremely common but remains astonishingly poorly perceived, 1–5 despite being a risk factor and a correlate or surrogate for the many pathologic conditions systematized in Table I. Its ECG manifestation is simple: P waves ≥110 ms duration (Figs.…”