Abbreviations legend: HT – arterial hypertension, DM – diabetes mellitus, CKD – chronic kidney disease, IHD – ischemic heart disease, HF – heart failure.
In one-way analysis it turned out that the duration of the P wave has a statistically significant relationship with the diagnosis (AF = 0, CV = 1) as well as hypertension and chronic kidney disease. Due to the possibility of a strong correlation between these parameters, a multifactorial (progressive stepwise) regression analysis was performed. As a result, the following model was obtained:
Mean P wave duration = 120.3 + 15.8 * CV + 20.2 *CKD + 9.0 * HT ± 18.5
The factors (stimulants) of longer duration of the P wave turned out to be: belonging to the CV group, the presence of chronic kidney disease and hypertension. All structural parameters of the model are statistically significant (p <0.0001): F (3, 115) = 12.6; p <0.001.
The duration of the P wave can be regarded as a parameter enabling classification of patients into the CV or AF group. Analysis of the ROC curve (Receiver Operating Characteristic curve) showed that for the cut-off value P wave duration> 148 ms the diagnostic sensitivity of the test was 67.7%, specificity 66.7% and the area under the ROC curve, AUC = 0.700. This is not a sensational result, but the lower confidence limit for AUC is 0.609 and is greater than 0.5 - this indicates the diagnostic usefulness of this parameter. According to the literature, if the AUC is in the range of 0.7 to 0.8, the classifier is satisfactory. The graphic presentation was depicted in Figure 5.