The study population consisted of a total of a 147 patients with EPS-defined diagnosis of cavotricuspid isthmus-dependent atrial flutter. 90.5% of these patients had a counterclockwise pattern of atrial activation, while 9.5% had a clockwise pattern. Twenty-three patients (16%) had unusual 12-lead ECG characteristics.
The mean age was 60 ± 13 years of age with a male predominance (85.7%). The mean left ventricular ejection fraction was 56.0± 14%. There was a high prevalence of prior manifest atrial fibrillation (23.8%), structural heart disease (36.7%), left atrial enlargement (24%), and previous cardiothoracic surgery (49.7%). All patient characteristics are shown in .
Comparison of baseline Characteristics, stratified by ECG pattern
Comparative analysis of baseline characteristics based on usual versus unusual ECG criteria demonstrate multiple significant characteristics. Patients with unusual ECG characteristics had a lower ejection fraction (50 ±16 versus 57 ±13, p=0.03), were more likely to have congestive heart failure (34.8% versus 12.1 %, p=0.006), more frequently manifest a clockwise pattern on EPS (34.8% versus 4.8%, p<0.005), and had longer atrial cycle lengths (mean CL 286 ±38 versus 254 ±31 msec, p=<0.005).
Unusual ECG Form
For the entire group of unusual ECG patterns (n=23), the most common unusual pattern was diffuse low amplitude flattening of the flutter wave in I, aVL, V5/6 in 13/23 (57%) of the cases (). Flattening was also seen in the inferior leads but at a much lower rate, 10/23 (43%). The morphology in V1 was variable with 10/23 (43%) revealing positive flutter waves (), (5/23) 22% flat, and (4/23) 17% fractionated (poorly defined low amplitude signals). Many of the unusual patterns seen mimic atrial fibrillation.
Figure 2 12 lead ECG of the unusual pattern seen in CTI flutter. Note the diffuse low amplitude flutter waves seen in most leads, but especially prominent in leads I, V5/6. The ECG is recorded at 25 mm/sec with a 1 mV/cm voltage. Note that the low amplitude tracing (more ...)
Figure 3 12 lead electrocardiogram of an unusual pattern seen in clockwise CTI dependent atrial flutter. Note the positive flutter waves seen in both V1 and the inferior leads (arrows). The flutter wave in V1 is biphasic with an initial positive deflection followed (more ...)
In the subgroup of patients with a clockwise activation pattern (n=8), 5/8 (63%) revealed flattening of the flutter wave in I, aVL, V5/6 and 3/8 (38%) in the inferior leads. There was no clear dominant pattern in V1, with the highest percentage being fractionated 3/8 (38%). Other patterns included positive flutter waves in both V1 and the inferior leads 1/8 (12.5%, see ) and positive flutter waves in V1 along with prolonged duration of biphasic flutter waves with curtailed diastolic interval in the inferior leads (3/8, 38%, ).
Figure 4 12 lead electrocardiogram of a pattern seen in clockwise CTI dependent atrial flutter, 3/8 patients. Note the positive flutter waves seen in V1 (vertical arrows) and the prolonged duration of biphasic flutter waves with curtailed diastolic interval in (more ...)
In patients with reduced systolic function (n=11), the flattening in the lateral leads was even more prominent with 8/11 (73%) of patients having flattening of the flutter waves in V5/6. V1 was more variable with the most common finding of a fractionated potential 3/11 (27%).
Univariate analayses of baseline and echocardiography provide three statistically significant predictors of unusual ECG flutter wave patterns. These include reduced ejection fraction (EF<55%) (RR of 2.2, p=0.033), congestive heart failure (RR of 2.88, p=0.006), and clockwise pattern on EPS (RR 5.1 and p<0.005). Severely reduced ejection fraction (EF<35%) had a relative risk of 1.85, but was not statistically significant (p=0.22). All relative risk ratios are shown in .
Univariate Analysis, Relative Risk ratio for Unusual ECG pattern
Of the three statistically significant variables demonstrated by univariate analysis, only two variables remained statistically significant in multivariate analysis (). These were reduced ejection fraction (OR 3.5, p=0.037) and CW pattern on EPS (OR 15.3, p<0.005). Although a clinical diagnosis of congestive heart failure was significant in univariate analysis, it failed to reach statistical significance by multivariate analysis (p=0.25).
Multivariate Analysis of variables that were significant by univarate assessment for an unusual surface ECG pattern.