192 Chapter 6 Proposed ECG course in classical FD patients Figure 1 is based on comparing absolute values of the ECG parameters of FD patients versus control subjects from the general population (chapter 3). To ensure a valid comparison, a group with a comparable number of CV risk factors as the FD cohort was chosen. With this approach, we gained more insight into the more Fabry-specific ECG changes [24]. The ECG alterations related to changes in the LV myocardium (negative frontal QRS-axis and increased Cornell index) were found to be the earliest altered ECG parameters in FD in patients. In a substantial proportion of patients with an increased Cornell index, LVMi on CMR was still normal, indicating that an abnormal Cornell index could be a precursor to visible LV thickening on conventional imaging and that this specific alteration may be related to subtle ultra-anatomical LV myocardial cell changes or that the reference values for LVH detection need to be adjusted for each sex and age group [25]. Accelerated AV-conduction time (shortened PR-interval) was observed in female patients up to the fifth decade, whereas in male patients the absolute value or increment in PR-interval was not different from controls. This suggests that the rate of change in atrial depolarization time in adult male patients is less suitable for monitoring heart disease development in FD, and a short PR-interval in an adult female patient could indicate the onset of cardiac FD involvement. As opposed to the common idea that a pathognomonic shortened PR-interval is present in FD, the absolute values of the PR-interval in the studied FD patients were often within the normal range of 120-200 milliseconds [26]. This finding was in agreement with the results reported by Namdar et al., who showed that a shortened PR-interval was not a frequent electrocardiographic finding (14%) in newly diagnosed adult patients (age: 40 ± 14 years) [27]. It can thus be concluded that a normal PR- interval does not exclude cardiac involvement in adult FD patients (particularly in male patients with FD and female FD patients over 50 years of age). Later in life, PR-interval shortening disappears in women with FD, and is replaced by a prolonged P- wave duration, which is an indicator of atrial enlargement [28]. Other abnormalities in LV conduction times (QRS-duration and QTc) and depolarization-repolarization interaction (frontal T-axis and spatial QRS-T angle) were observed in women with FD from the fifth decade onwards, and in men from the fourth decade onwards. It can be deduced that abnormalities in ECG parameters reflecting early LV myocardium alterations appear two decades before the occurrence of cardiac complications and that markers representing LV depolarisation-repolarisation become apparent one decade prior cardiac complications’ onset.
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