Background: While P‐wave duration (P‐dur) and dispersion (P‐disp) could both reflect fractionated and inhomogeneous propagation of sinus cardiac impulses, and may therefore be associated with each other, a clear relationship has not been extensively studied. We studied these markers as well as the significance of P‐wave terminal force in lead V1 (PTFV1) in relation to the P‐wave axis (P‐axis). Methods: We appraised our previously studied sample of 500 consecutively numbered, otherwise unselected, electrocardiograms (ECGs) of outpatients from the University of Massachusetts, Worcester, Massachusetts, for the foregoing P‐wave characteristics. P‐disp, defined as the difference of the duration between the widest and narrowest P wave, and the greatest P‐dur after a 12‐lead ECG search, was measured manually to the nearest 10 ms. PTFV1 was considered positive when ≥40 mm 2 terminal deflection was present on biphasic P waves on lead V 1 . Normal P‐axis was considered 0° to +75° by manually constructing the mean frontal plane electrical P‐axis from standard limb leads. Results: After excluding those with atrial arrhythmias, paced rhythms, errors in lead placement, P waves with low amplitude or overall technically poor tracing, 428 ECGs formed our final sample. P‐dur was strongly associated with P‐disp (P < 0.0001), but the correlation remained weak (r = 0.42). Overall, P‐dur was not significantly associated with P‐axis but when divided into tertiles and quintiles, the significance was evident within the range of the normal P‐axis, particularly 0° to +60° (P < 0.0001). In a subanalysis of 380 ECGs that had appreciable biphasic P waves on lead V 1 , PTFV1 was noted on 178 (47%) ECGs and was significantly associated with P‐dur (P < 0.0001), P‐disp (P < 0.0001), and P‐axis (P = 002). When considering P‐axis in tertiles and quintiles, P‐dur was greater in patients with a positive PTFV1 and significant within the normal range of the P‐axis, especially from 0° to +60°. Conclusion: P‐dur, P‐disp, and PTFV1 appear to share a significant tripartite association in relation to the normal P‐axis, particularly when P‐axis ranges 0° to +60°. Therefore, for optimal clinical assessment, these markers should be evaluated in relation to the normal P‐axis.
A 35 year-old asymptomatic Caucasian female with a family history of hypertrophic cardiomyopathy (HCM) was referred for cardiologic evaluation. The electrocardiogram and transthoracic echocardiogram were normal. Cardiovascular magnetic resonance (CMR) was performed for further assessment of myocardial function and presence of myocardial scar. CMR showed normal left ventricular systolic size, measurements and function. However, there was extensive, diffuse late gadolinium enhancement (LGE) throughout the left ventricle. This finding was consistent with extensive myocardial scarring and was highly suggestive of advanced, non-ischemic cardiomyopathy. Genotyping showed a heterozygous mis-sense mutation (275G>A) in the cardiac troponin T (TNNT2) gene, which is causally associated with HCM. There have been no previous reports of such extensive, atypical pattern of myocardial scarring despite an otherwise structurally and functionally normal left ventricle in an asymptomatic individual with HCM. This finding has important implications for phenotype screening in HCM.
Abnormal atrial depolarization, denoted as interatrial block (IAB; P wave >110 ms), is associated with myocardial ischemia during exercise. The authors conducted an 18-month follow-up for cardiovascular events in 31 consecutive patients with IAB and 60 controls without IAB at rest; participants had coronary artery disease and hypertension and had undergone coronary angiography following positive exercise tolerance test (ETT) results. Atrial fibrillation and need for repeat ETT and coronary artery revascularization were significant with IAB (77.4% vs 20%; P<.001). In patients with such events, IAB, left atrial dilatation, left ventricular hypertrophy, increased left ventricular end-diastolic volume, poorer Duke prognostic treadmill (DPT) scores, and significant coronary artery stenoses were predominant. IAB (hazard ratio [HR], 4.9; 95% confidence interval [CI], 1.3-19.7; P=.02) and DPT scores (HR, 0.84; 95% CI, 0.72-0.98; P=.03) were independently associated with these events. At 18 months' follow-up, IAB at rest was associated with cardiovascular events among those with known coronary artery disease and hypertension.
Tako-Tsubo cardiomyopathy (TTC), also known as transient left ventricular apical ballooning syndrome,1 is a reversible, stress-induced cardiomyopathy that predominantly affects post-menopausal, elderly women during emotional or physical stress.1,2 Although it is an increasingly recognized and reported syndrome, the syndrome remains uncommon, occurring in <1% of patients referred for coronary angiogram.
Interatrial block (IAB; P wave > or =110 ms), a conduction delay between the right and left atria (LA), is highly prevalent and strongly associated with atrial tachyarrhythmias, LA electromechanical dysfunction as well as a risk of embolism. Nonetheless, clinicians' underappreciation of its existence and sequelae remains. We appraised this issue in a general hospital population.From the database of 730 12-lead electrocardiograms (ECGs) of patients aged 17-98 years (mean age 67.80 years; female patients 53.56%) in a tertiary care teaching general hospital, we recorded the computer-generated diagnostic readings of the ECGs and also the official cardiologist and hospitalist ECG interpretations and documentations. For increased sensitivity and specificity, and because the mode P wave duration in IAB is 120 ms, P waves > or =120 ms in any lead were used to diagnose IAB.Six hundred and fifty-three ECGs (89.45%) showed sinus rhythm, and of those, IAB was documented on 309 ECGs (47.32%). LA enlargement was cited 29 times (3.97%), while possible LA enlargement and biatrial enlargement were cited 17 (2.32%) and 6 times (0.82%), respectively. One cardiologist's ECG interpretation documented IAB (0.32%), but none of the other medical staff diagnosed IAB or abnormal P wave duration.This study demonstrates to extremes how IAB went undiagnosed in a general hospital population. Until more awareness of IAB is cultivated, such ignorance of the existence and sequelae of IAB could continue. Configuring ECG software to include P wave durations in computer-generated ECG readings could be useful in aiding diagnosis.
5-fluorouracil (5-FU) is a fluorinated, pyrimidine analog, antineoplastic agent that is used in the treatment of several solid organ cancers. Cardiotoxicity is uncommon but life-threatening manifestations such as myocardial infarction may manifest owing to 5-FU-induced coronary artery spasm. Administering smaller doses of the drug, more frequently than not, decreases the risk of cardiotoxicity compared to large doses or with continuous infusions. We present a case of ST-segment elevation in a patient without known coronary artery disease who had presented following continuous 5-FU infusion. Coronary angiogram confirmed absence of coronary artery disease and intravenous calcium channel blockers administration was commensurate with the patient’s improvement in symptoms. We discuss the literature on 5-FU and its association with coronary artery spasm, and also briefly review chemotherapy-induced cardiotoxicities to help better prepare internists and other primary health care providers to face similar challenges, particularly of the uncommon but potentially life-threatening manifestations.
