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The Cardiovascular Atlas

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CVD Atlas

Recognizing left bundle branch block (LBBB) on two different paper speeds.

Dr Araz Rawshani, MD, PhD

Associate professor Department of Cardiology, Sahlgrenska University Hospital, Sweden Institute of Medicine, Department of Molecular and Clinical Medicine, Gothenburg, Sweden
More by Dr Araz Rawshani, MD, PhD

Figure 4. It is easy to recognize LBBB on 25 mm/s and 50 mm/s. Use large squares to estimate the QRS duration as shown in this illustration. Recall that at paper speed 25 mm/s, one large square equals 200 ms and one small square equals 40 ms. Thus, on 25 mm/s 3 small squares equals 120 ms. On paper speed 50 mm/s one large square equals 100 ms and one small square equals 20 ms. Thus, at 50 mm/s one large plus one small square equals 120 ms.

Figure 4. It is easy to recognize LBBB on 25 mm/s and 50 mm/s. Use large squares to estimate the QRS duration as shown in this illustration. Recall that at paper speed 25 mm/s, one large square equals 200 ms and one small square equals 40 ms. Thus, on 25 mm/s 3 small squares equals 120 ms. On paper speed 50 mm/s one large square equals 100 ms and one small square equals 20 ms. Thus, at 50 mm/s one large plus one small square equals 120 ms.

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