Age-related changes in P wave morphology in healthy subjects

<p>Abstract</p> <p>Background</p> <p>We have previously documented significant differences in orthogonal P wave morphology between patients with and without paroxysmal atrial fibrillation (PAF). However, there exists little data concerning normal P wave morphology. This study was aimed at exploring orthogonal P wave morphology and its variations in healthy subjects.</p> <p>Methods</p> <p>120 healthy volunteers were included, evenly distributed in decades from 20–80 years of age; 60 men (age 50+/-17) and 60 women (50+/-16). Six-minute long 12-lead ECG registrations were acquired and transformed into orthogonal leads. Using a previously described P wave triggered P wave signal averaging method we were able to compare similarities and differences in P wave morphologies.</p> <p>Results</p> <p>Orthogonal P wave morphology in healthy individuals was predominately positive in Leads X and Y. In Lead Z, one third had negative morphology and two-thirds a biphasic one with a transition from negative to positive. The latter P wave morphology type was significantly more common after the age of 50 (P < 0.01). P wave duration (PWD) increased with age being slightly longer in subjects older than 50 (121+/-13 ms vs. 128+/-12 ms, P < 0.005). Minimal intraindividual variation of P wave morphology was observed.</p> <p>Conclusion</p> <p>Changes of signal averaged orthogonal P wave morphology (biphasic signal in Lead Z), earlier reported in PAF patients, are common in healthy subjects and appear predominantly after the age of 50. Subtle age-related prolongation of PWD is unlikely to be sufficient as a sole explanation of this finding that is thought to represent interatrial conduction disturbances. To serve as future reference, P wave morphology parameters of the healthy subjects are provided.</p

Revisiting QRS detection methodologies for portable, wearable, battery-operated, and wireless ECG systems

Cardiovascular diseases are the number one cause of death worldwide. Currently, portable battery-operated systems such as mobile phones with wireless ECG sensors have the potential to be used in continuous cardiac function assessment that can be easily integrated into daily life. These portable point-of-care diagnostic systems can therefore help unveil and treat cardiovascular diseases. The basis for ECG analysis is a robust detection of the prominent QRS complex, as well as other ECG signal characteristics. However, it is not clear from the literature which ECG analysis algorithms are suited for an implementation on a mobile device. We investigate current QRS detection algorithms based on three assessment criteria: 1) robustness to noise, 2) parameter choice, and 3) numerical efficiency, in order to target a universal fast-robust detector. Furthermore, existing QRS detection algorithms may provide an acceptable solution only on small segments of ECG signals, within a certain amplitude range, or amid particular types of arrhythmia and/or noise. These issues are discussed in the context of a comparison with the most conventional algorithms, followed by future recommendations for developing reliable QRS detection schemes suitable for implementation on battery-operated mobile devices.Mohamed Elgendi, Björn Eskofier, Socrates Dokos, Derek Abbot

QRS score versus ST-segment changes in patients undergoing TI-201 scintigraphy using dipyridarnole infusion

Background. ST-segment changes after dipyridamole infusion followed by handgrip isometric stress lack diagnostic value, because of the low sensitivity for the detection of coronary artery disease (CAD). In addition, an abnormal QRS score during exercise had a greater diagnostic ability than ST-segment changes to detect CAD. This study was undertaken to compare QRS score values with ST-segment changes during thallium 201 scintigraphy via dipyridamole infusion. Methods and Results. In this study 128 patients (101 men and 27 women), aged 53 to 72 years (mean, 59 +/- 8 years), underwent TI-201 scintigraphy after dipyridamole infusion and handgrip isometric stress, as well as coronary angiography. QRS score values and ST-segment changes after dipyridamole infusion and handgrip isometric stress were also estimated. CAD was detected in 96 patients (75%), whereas normal coronary arteries were found in 32 (25%). According to scintigraphic data, 48 patients (37%) had no reversible perfusion defects whereas 80 (63%) had at least 1 reversible perfusion defect. Sensitivities for an abnormal QRS score and ST-segment deviation were 68% versus 18% (P &lt; .01) for detection of CAD and 75% versus 19% for detection of myocardial ischernia (P &lt; .01), respectively. Similar specificities were found (P = not significant). Conclusions. An abnormal QRS score significantly improves the low sensitivity of ST-segment changes for the detection of myocardial ischemia and CAD by use of TI-201 scintigraphy with dipyridamole infusion and handgrip isometric stress

Assessment of time domain and spectral components of heart rate variability immediately before ischemic ST segment depression episodes

In an attempt to study autonomic function during the 5-minute period preceding ischemic ST segment depression (down arrow ST) episodes, we selected 138 down arrow ST episodes, without preceding down arrow ST during the last 15 minutes before each episode, from the Holter tapes of 35 patients with multivessel coronary artery disease. For the 5-minute period preceding each down arrow ST episode, we calculated the following heart rate variability (HRV) indices; the mean RR interval (RR5), the standard deviation of all RR intervals (SD Index5), the corresponding coefficient of variation (CV5), and the natural log (Ln) of the spectral components, total power at 0.000 to 0.400 Hz (TP5), low frequency power at 0.040 to 0.150 Hz (LF5), high frequency power at 0.150 to 0.400 Hz (HF5), and the ratio of the low to high frequency power (LF5/HF5). As HRV indices of the 24-hour period, we calculated the respective RR, SD Index, CV, Ln TP, LnLF, LnHF, and Ln LF/HF. RR5, SD Index5, CV5, and Ln TP5 were all significantly lower than RR (t = -5.343, p = 3.7 x 10(-7)), SD index (t = -19.091, p = 1.99 x 10(-40)), CV(t = -15.780, p = 1.28 x 10(-32)), and LnTP (t = -3.210, p = 0.0016), respectively. LnHF5 was inversely correlated with the magnitude of the down arrow ST; r = -0.174, P &lt; 0.05, and CV5 was inversely correlated with the natural log (Ln) of the ischemic event duration; r = -0.183, P ( 0.05. Analogous results were obtained for both the painful and silent down arrow ST episodes. It is concluded that HRV is decreased during the 5-minute period preceding down arrow ST episodes, and is inversely related with the magnitude and the duration of the down arrow ST

Ischemia-induced reflex sympathoexcitation during the recovery period after maximal treadmill exercise testing

Background: Heart rate variability (HRV) analysis is problematic during maximal treadmill exercise testing (ET) due to rapidly changing heart rate. Hypothesis: The aim of this study was to assess HRV spectral components during treadmill ET in patients with coronary artery disease (CAD) and in healthy controls, and to search for possible differences between the two groups, Methods: Thirty patients with CAD and 30 age-matched healthy controls underwent symptom-limited ET and continuous electrocardiographic monitoring. For adequate assessment of HRV during maximal ET, we calculated the HRV measures [normalized units (NU)]-low-frequency (0.040-0.150 Hz) power (LF), high-frequency (0.150-0.400 Hz) power (HF), and the LF/HF ratio-from all the sequential stages of the ET with Limited changes (20 beats/min) in heart rate (stress 80-100, 100-120, 120-140, 140-160, 160-180/recovery 180-160, 160-140, 140-120, 120-100, 100-80). Results: Both LF and HF were found to decrease gradually during ET and to increase during the recovery period in both patients and controls (p&lt;0.001). LF values were higher during the recovery period than during the respective stages of exercise time in both patients and controls, and LF/HF ratio was higher during recovery in patients only. Conclusions: During maximal ET (1) vagal tone withdraws during the exercise time and increases during the recovery period; (2) the sympathetic activity predominates during the recovery period, especially in patients with CAD and exercise-induced myocardial ischemia, This finding raises the possibility of ischemia-induced cardiocardiac sympathetic excitatory reflexes