ECG Tracing: Between Waves and Intervals (Part 2)
A Nasiff Associates ECG Machine Brand Review

As the second part of the ECG Tracing: Between Waves and Intervals article series, we will now be discussing the other component of ECG tracing which is called QRS complex, for we have already discussed the first component which is the P wave.

The QRS Complex Overview

The QRS complex is a structure on the ECG that corresponds to the depolarization of the ventricles. Because the ventricles contain more muscle mass than the atria, the QRS complex is larger than the P wave. In addition, because the His/Purkinje system coordinates the depolarization of the ventricles, the QRS complex tends to look "spiked" rather than rounded due to the increase in conduction velocity. A normal QRS complex is 0.08 to 0.12 sec (80 to 120 ms) in duration represented by three small squares or less, but any abnormality of conduction takes longer, and causes widened QRS complexes.

Not every QRS complex contains a Q wave, an R wave, and an S wave. By convention, any combination of these waves can be referred to as a QRS complex. However, correct interpretation of difficult ECGs requires exact labeling of the various waves. Some authors use lowercase and capital letters, depending on the relative size of each wave. For example, an Rs complex would be positively deflected, while a rS complex would be negatively deflected. If both complexes were labeled RS, it would be impossible to appreciate this distinction without viewing the actual results from the ECG machine.

• The duration, amplitude, and morphology of the QRS complex is useful in diagnosing cardiac arrhythmias, conduction abnormalities, ventricular hypertrophy, myocardial infarction, electrolyte derangements, and other disease states.
• Q waves can be normal (physiological) or pathological. Pathological Q waves refer to Q waves that have a height of 25% or more than that of the partner R wave and/or have a width of greater than 0.04 seconds. Normal Q waves, when present, represent depolarization of the interventricular septum. For this reason, they are referred to as septal Q waves, and can be appreciated in the lateral leads I, aVL, V5 and V6.
• Q waves greater than 1/4 the height of the R wave, greater than 0.04 sec (40 ms) in duration, or in the right precordial leads are considered to be abnormal, and may represent myocardial infarction.
• "Buried" inside the QRS wave is the atrial repolarization wave, which resembles an inverse P wave. It is far smaller in magnitude than the QRS and is therefore obscured by it.

Yet another information overload, huh? Well anyway, let’s get back again to EKGShop.Com, as we introduce again another remarkable EKG Machine brand, which is the Nasiff Associates.

Below are the products that are featured in the EKGShop.Com website:

Nasiff PC-Based Interpretive EKG - PC Based Interpretive 12-Lead Resting ECG. This machine pays for itself after 75 tests. Simultaneous Interpretive 12 Lead Acquisitions of your PC ECG / PC EKG. ECG Interpretation classes: MIs, Blocks, Enlargements, Axis. Over 100 calls. WINDOWS: Easy Point & Click User Interface. Real-Time 12, 6, 3, 2 or 1 ECG Lead Color Display of ECG / EKG Complex.

Nasiff Cardio PC based Stress ECG - Nasiff Cardio-Suite Combined 12-Lead Interpretive ECG. This machine pays for itself after 175 tests. Cardio Card STRESS ECG System. Includes, Cardio Card RESTING Interpretive PC ECG System. All managed by a Central Integrated Seamless DataBase Management System.

Established in 1989 to develop the world's first PC ECG / PC EKG, Nasiff Associates, a Medical Technology Company, is committed to providing Medical PC Solutions to Health Care Professionals by developing Medical Diagnostic and Administrative products, which integrate into any Personal Computer (PC).