Both the American Clinical Neurophysiology Society ^{Reference Sinha, Sullivan and Sabau1} and the Canadian Society of Clinical Neurophysiologists ^{Reference Dash, Dash and Primrose2} recommend that a single channel electrocardiogram (ECG) should be included as an extra channel of the electroencephalogram (EEG) recording, principally to detect contamination of EEG by apiculate waveforms, pulse artifact, or movement artifact.

However, another value of recording and interpreting the ECG, as part of the EEG record, ^{Reference Kendirli, Aparci and Kendirli3} is the detection of arrhythmias, notably atrial fibrillation (AF) ^{Reference Bontempo and Goralnick4} and pauses, as might occur in sick sinus syndrome or conduction block, which may be relevant in the differentiation of syncope versus seizures. ^{Reference Viljoen, Smith and Chin5}

The detection of AF is of great clinical importance. ^{Reference Kirchhof, Benussi and Kotecha6} AF is the commonest cardiac arrhythmia in the general population, and it frequently indicates underlying heart disease and poses an important risk for cardiogenic stroke, other systemic embolism, myocardial infarction, heart failure, and increased mortality. ^{Reference Odutayo, Wong, Hsaio, Hopewell, Altman and Emdin7,Reference Boriani and Proietti8} Recognition of AF and consequent appropriate therapy can prevent or ameliorate much of its associated morbidity and mortality. ^{Reference Yaghi and Kamel9,Reference Boriani, Diemberger, Martignani, Biffi and Branzi10}

The incidence of AF is age-dependent, with an abrupt increase after age 65, rising to over 10% of persons over 80 years. ^{Reference Andrade, Khairy, Dobrev and Nattel11} AF can also occur in young adults, especially in those with hypertension, hyperthyroidism, valvular heart disease, and with lifestyle factors such as smoking and abuse of alcohol and recreational pharmaceuticals. ^{Reference Aggarwal, Selvendran, Raphael and Vassiliou12} Therefore, special attention is needed to record and accurately interpret the ECG channel in high-risk groups.

We undertook a review of the prevalence of AF as recorded and interpreted, as part of the EEG report, by GBY in over 4500 records from our EEG laboratories over 7 years. The purpose was to show the prevalence of AF in various age groups in patients referred to a community EEG laboratory in Canada.

Methods

All recordings were done with Natus EEG technology, with 18 channels of EEG and 1 ECG channel (long lead I) recording with a sampling rate of 240 Hz/channel and low and high frequency filter settings at 1 and 70 Hz, respectively. Recordings were 20 min in duration.

The study size of 4529 EEG reports included patients from 0 to 100 years of age, with the first EEG report dating back to early 2013. These included consecutive reports over 7 years reported by GBY. Only one recording per patient was considered. The EEG reports were reviewed, rather than the actual traces. Several recordings were reviewed to select suitable figures for the paper. Grouping of the reports was made based on the decade of age at the time of the EEG recording. For each report, age, gender, and occurrence of AF were noted. With the grouping of the reports based on the decade established, the number of patients noted to have AF was determined and calculated as an overall percentage of each age category.

AF was diagnosed when there were no “p waves” in the ECG trace and the R−R interval was irregularly irregular, compatible with ACC/AHA Guidelines. ^{Reference Fuster, Ryden and Cannom13} Atrial flutter was included as AF, as their clinical significance is similar and the two rhythms often occur in the same individual. ^{Reference Fuster, Ryden and Cannom13} Examples of recordings showing AF/atrial flutter are shown in Figure 1.

FIGURE 1: (A) is a recording from an 81-year-old man who developed encephalopathy while in hospital. The recording is of low voltage showing a predominance of beta activity and some electrode artifacts related to perspiration. The ECG channel shows atrial fibrillation with a minor interventricular conduction defect. (B) is from an 89-year-old woman with impaired consciousness. The EEG shows diffuse slowing and ECG channel shows atrial fibrillation with an ectopic beat. (C) is of an 89-year-old woman with “confusion.” There is excessive beta activity and slowing in the delta range in the left posterior head. The ECG channel shows rapid atrial fibrillation. (D) is of an 82-year-old man with abnormal mental status. There is intermittent focal slowing in the left posterior head. The ECG shows atrial fibrillation with occasional premature ventricular beats.

Results

The 7-year spread of EEG reports comprised 4529 patients, 43 of whom had AF. As shown in Table 1, there were a total of two cases of AF between the ages of 0 and 60 out of a total of 2948 EEG reports. The remaining 41 cases of AF were seen in patients above the age of 60, out of the remaining 1580 reports (Figure 2). Of the 43 patients with AF, 29 were male and 14 were female. Note that the female to male ratio increases in older age groups (Figure 3).

FIGURE 2: The percentage of atrial fibrillation per decade.

FIGURE 3: The number of cases AF per decade as related to gender.

Table 1: Prevalence of atrial fibrillation in each decade

Overall prevalence of AF in each grouping of decade is shown in Table 1 and Figure 2. Throughout the first 60 years of life, there is an insignificant prevalence of AF, with a couple of cases in a few of the decades. However, it is seen that past the age of 60, the prevalence of AF rises almost exponentially. The initial notable change in prevalence is seen in the rise from 0% to 0.9% between the (50s) and (60s) age grouping. This figure continues to increase, eventually reaching a value of 8% prevalence in the 90–100 age category.

The most significant increase of AF prevalence is noted in the rise from the 60–69 to the 70–79 age group, with a 200% increase in the 70s decade compared to the 60s decade. However, the decades onwards demonstrate a slower rate of growth with an 85% increase from the 70s to the 80s, and a 60% increase from the 80s to the 90s.