Estimated Local Conduction Velocity in Atrial Flutter
Estimated Local Conduction Velocity in Atrial Flutter
Background: Low conduction velocity (CV) in the area showing low electrogram amplitude (EA) is characteristic of reentry circuit of atypical atrial flutter (AFL). The quantitative relationship between CV and EA remains unclear. We characterized AFL reentry circuit in the right atrium (RA), focusing on the relationship between local CV and bipolar EA on the circuit.
Methods and Results: We investigated 26 RA AFL (10 with typical AFL; 10 atypical incisional AFL; 6 atypical nonincisional AFL) using CARTO system. By referring to isochronal and propagation maps delineated during AFL, points activated faster on the circuit were selected (median, 7 per circuit). At the 196 selected points obtained from all patients, local CV measured between the adjacent points and bipolar EA were analyzed. There was a highly significant correlation between local CV and natural logarithm of EA (lnEA) (R = 0.809, P < 0.001). Among 26 AFL, linear regression analysis of mean CV, calculated by dividing circuit length (152.3 ± 41.7 mm) by tachycardia cycle length (TCL) (median 246 msec), and mean lnEA, calculated by dividing area under curve of lnEA during one tachycardia cycle by TCL, showed y = 0.695 + 0.191x (where: y = mean CV, x = lnEA; R = 0.993, P < 0.001). Local CV estimated from EA with the use of this formula showed a highly significant linear correlation with that measured by the map (R = 0.809, P < 0.001).
Conclusion: The lnEA and estimated local CV show a highly positive linear correlation. CV is possibly estimated by EA measured by CARTO mapping.
Reentry is possible when the circuit with the path length longer than or equal to the excitation wavelength, the product of the conduction velocity (CV) and the refractory period, is present. In typical, cavotricuspid isthmus-dependent atrial flutter (AFL), the circuit length is long, so that the excitation wavefront is allowed to travel around the tricuspid annulus at the normal CV. The circuit size of atypical AFL, however, is considered to be much smaller than that of typical AFL, and thus the wavelength needs to be shorter. A short wavelength can be achieved by slowing of the CV along the circuit and/or shortening of the refractory period. In fact, the circuit of atypical AFL often involves the electrically abnormal area that allows slow conduction. Furthermore, in the critical isthmus within the circuit, low amplitude and fractionated electrogram is frequently observed.
The electrically abnormal lesion has been defined as an area with the bipolar electrogram amplitude (EA) <0.5 mV in the atrium. Local CV was reported to be significantly low in the electrically abnormal lesion with the amplitude <0.5 mV in patients with atrial fibrillation. In the reentry circuit of AFL, however, the detailed relationship between the CV and EA has not been clarified yet. We hypothesized that there is a positive correlation between the local CV and peak-to-peak bipolar EA in the atrial tissue. To test this hypothesis, we performed the high-density electroanatomical mapping (EAM) during typical and atypical AFL in the right atrium (RA), and by selecting mapping points on the circuit, we estimated the local CV and examined its relationship with bipolar EA.
Abstract and Introduction
Abstract
Background: Low conduction velocity (CV) in the area showing low electrogram amplitude (EA) is characteristic of reentry circuit of atypical atrial flutter (AFL). The quantitative relationship between CV and EA remains unclear. We characterized AFL reentry circuit in the right atrium (RA), focusing on the relationship between local CV and bipolar EA on the circuit.
Methods and Results: We investigated 26 RA AFL (10 with typical AFL; 10 atypical incisional AFL; 6 atypical nonincisional AFL) using CARTO system. By referring to isochronal and propagation maps delineated during AFL, points activated faster on the circuit were selected (median, 7 per circuit). At the 196 selected points obtained from all patients, local CV measured between the adjacent points and bipolar EA were analyzed. There was a highly significant correlation between local CV and natural logarithm of EA (lnEA) (R = 0.809, P < 0.001). Among 26 AFL, linear regression analysis of mean CV, calculated by dividing circuit length (152.3 ± 41.7 mm) by tachycardia cycle length (TCL) (median 246 msec), and mean lnEA, calculated by dividing area under curve of lnEA during one tachycardia cycle by TCL, showed y = 0.695 + 0.191x (where: y = mean CV, x = lnEA; R = 0.993, P < 0.001). Local CV estimated from EA with the use of this formula showed a highly significant linear correlation with that measured by the map (R = 0.809, P < 0.001).
Conclusion: The lnEA and estimated local CV show a highly positive linear correlation. CV is possibly estimated by EA measured by CARTO mapping.
Introduction
Reentry is possible when the circuit with the path length longer than or equal to the excitation wavelength, the product of the conduction velocity (CV) and the refractory period, is present. In typical, cavotricuspid isthmus-dependent atrial flutter (AFL), the circuit length is long, so that the excitation wavefront is allowed to travel around the tricuspid annulus at the normal CV. The circuit size of atypical AFL, however, is considered to be much smaller than that of typical AFL, and thus the wavelength needs to be shorter. A short wavelength can be achieved by slowing of the CV along the circuit and/or shortening of the refractory period. In fact, the circuit of atypical AFL often involves the electrically abnormal area that allows slow conduction. Furthermore, in the critical isthmus within the circuit, low amplitude and fractionated electrogram is frequently observed.
The electrically abnormal lesion has been defined as an area with the bipolar electrogram amplitude (EA) <0.5 mV in the atrium. Local CV was reported to be significantly low in the electrically abnormal lesion with the amplitude <0.5 mV in patients with atrial fibrillation. In the reentry circuit of AFL, however, the detailed relationship between the CV and EA has not been clarified yet. We hypothesized that there is a positive correlation between the local CV and peak-to-peak bipolar EA in the atrial tissue. To test this hypothesis, we performed the high-density electroanatomical mapping (EAM) during typical and atypical AFL in the right atrium (RA), and by selecting mapping points on the circuit, we estimated the local CV and examined its relationship with bipolar EA.