Abnormal and normal Q waves in inferior ECG leads

Mehdi, Saba Ali Jasab

5. Term (Master thesis)

Medicine, Master

2015

2015-12-21

22

Baggrund: Q-takker i et elektrokardiogram (EKG) kan tyde på tidligere hjerteskade. En Q-tak betegnes ofte som patologisk, når den både er dyb (høj amplitude) og bred (lang varighed). Det er uklart, hvordan hver af disse egenskaber hver for sig påvirker prognosen, når Q-takken ses i de inferiore afledninger (II, III og aVF), som afspejler hjertets nedre del. Formål: At undersøge sammenhængen mellem varighed og amplitude af Q-takker i de inferiore afledninger og dødelighed. Metoder: Ved hjælp af digitaliserede EKG’er identificerede vi tre gensidigt udelukkende populationer for at undersøge forskellige Q-tak-morfologier i afledning II, III og aVF og deres prognostiske betydning over 5 år. Oplysninger om diagnoser og udfald blev hentet fra danske registre. Vi anvendte multivariat justerede Cox-modeller til at estimere risikoen for død for mønstre, hvor kun varigheden var patologisk, kun amplituden var patologisk, eller begge dele var patologiske, med personer med normale Q-takker i den pågældende afledning som reference. Resultater: Vi inkluderede 36.645 personer for afledning II, 8.129 for afledning III og 42.892 for aVF. Femårs-dødeligheden var 9,1% (II), 15,7% (III) og 10,2% (aVF). En patologisk varighed alene var forbundet med højere dødelighed i afledning II (HR 1,48; 95% CI 1,08–2,02), i aVF (HR 1,17; 95% CI 1,05–1,29) og også i afledning III (HR 2,52; 95% CI 1,44–4,42). En patologisk amplitude alene var forbundet med højere dødelighed i afledning II (HR 1,36; 95% CI 1,20–1,55) og i aVF (HR 1,52; 95% CI 1,35–1,71). Som pejlemærke svarer en HR på 1,48 til ca. 48% højere relativ risiko sammenlignet med referencegruppen. Konklusion: Tilstedeværelsen af en Q-tak, der kun opfylder ét patologisk kriterium (varighed ≥ 30 ms eller amplitude ≥ 100 mV) i én inferior afledning (II eller aVF) ledsaget af en Q-tak, der opfylder begge kriterier (amplitude ≥ 100 mV og varighed ≥ 30 ms) i en anden inferior afledning, var forbundet med øget dødelighed. Resultaterne understøtter, at både varighed og amplitude af Q-takker i de inferiore afledninger har betydning for prognosen.

Background: Q waves on an electrocardiogram (ECG) can indicate prior heart injury. A Q wave is often called pathological when it is both deep (high amplitude) and wide (long duration). It is unclear how each feature, on its own, relates to prognosis when Q waves appear in the inferior leads (II, III, aVF), which view the lower part of the heart. Objective: To examine the association between Q-wave duration and amplitude in inferior leads and mortality. Methods: Using digital ECGs, we defined three mutually exclusive populations to study different Q-wave morphologies in leads II, III and aVF and their prognostic value over 5 years. Diagnoses and outcomes were obtained from Danish registries. We applied multivariable Cox proportional hazards models to estimate mortality risk for patterns where only duration was pathological, only amplitude was pathological, or both were pathological, using individuals with normal Q waves in the lead under study as the reference. Results: We included 36,645 individuals for lead II, 8,129 for lead III and 42,892 for lead aVF. Five-year mortality was 9.1% (II), 15.7% (III) and 10.2% (aVF). Pathological duration alone was associated with higher mortality in lead II (HR 1.48; 95% CI 1.08–2.02), in aVF (HR 1.17; 95% CI 1.05–1.29), and also in lead III (HR 2.52; 95% CI 1.44–4.42). Pathological amplitude alone was associated with higher mortality in lead II (HR 1.36; 95% CI 1.20–1.55) and in aVF (HR 1.52; 95% CI 1.35–1.71). For context, an HR of 1.48 corresponds to about a 48% higher relative risk compared with the reference group. Conclusions: The presence of a Q wave meeting only one pathological criterion (duration ≥ 30 ms or amplitude ≥ 100 mV) in one inferior lead (II or aVF), together with a Q wave meeting both criteria (amplitude ≥ 100 mV and duration ≥ 30 ms) in another inferior lead, was associated with increased mortality. These findings indicate that both Q-wave duration and amplitude in the inferior leads matter for prognosis.

[This abstract was generated with the help of AI]

Myokardieinfarkt ; Q-tak ; længde ; bredde

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