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The electrocardiogram during sinus rhythm and tachycardia in patients with Mahaim fibers

The importance of an "rS" pattern in lead III

Eduardo Back Sternick, MD^*,*, Carl Timmermans, MD, Eduardo Sosa, MD, Fernando E.S. Cruz, MD, FACC, Luz-Maria Rodriguez, MD, FACC, Márcio Fagundes, MD, Luiz M. Gerken, MD^* and Hein J.J. Wellens, MD, FACC

^* Biocor Instituto, Belo Horizonte, Brazil
University Hospital, Maastricht, Maastricht, The Netherlands
Instituto do Coração, Faculdade de Medicina, Universidade de São Paulo, São Paulo, Brazil
Instituto Nacional de Cardiologia Laranjeiras, Ministério da Saúde, Rio de Janeiro, Brazil

View larger version (71K): [in a new window]   Figure 1 Two patients with Mahaim fibers displaying the rS pattern in electrocardiographic lead III.

View larger version (57K): [in a new window]   Figure 2 Five-lead electrocardiogram during sinus rhythm with the pre-ablation electrocardiogram showing the rS pattern in four cases and rsR' in one patient. The post-ablation electrocardiogram shows a clear change in QRS configuration.

View larger version (204K): [in a new window]   Figure 3 (A) ECG showing minimal preexcitation (rsR' pattern in lead III) only in the first three QRS complexes. (B) Electrocardiogram after intravenous verapamil shows sinus rhythm with AV conduction over the Mahaim fiber with a long PR interval and overt pre-excitation.

View larger version (24K): [in a new window]   Figure 4 (Left) Patient no. 6 without preexcitation showing a shorter atrio-his interval (AH) than AM interval. (Right) Patient no. 2 showing an AM shorter than the AH interval, resulting in minimal preexcitation with an rS pattern in lead III.

View larger version (26K): [in a new window]   Figure 5 Case 29: this patient had an anterior Mahaim fiber and an intermediate QRS axis (50°) during sinus rhythm and antidromic tachycardia. There is a minimal preexcitation but without the rS pattern in lead III.

View larger version (19K): [in a new window]   Figure 6 Proportion of patients with an rS pattern in lead III during sinus rhythmin relation to the location of the atrial end of the Mahaim fiber along the tricuspid annulus. CS = coronary sinus; MS = mid-septal; RA = right anterior; RAL = right anterolateral; RL = right lateral; RP = right posterior; RPL = right posterolateral.

View larger version (20K): [in a new window]   Figure 7 Lead III pattern in 200 young individuals with palpitations.