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Clinical Reasoning and Diagnostic Errors
Published in Paul Cerrato, John Halamka, Reinventing Clinical Decision Support, 2020
Nor are these prerequisites always required to arrive at an accurate diagnosis. In fact, the best clinicians have learned to integrate Type 1 and Type 2 reasoning into their cognitive “toolkit,” and to switch back and forth between the 2 as needed. By way of illustration, consider the diagnostic process required to distinguish non–ST segment elevation myocardial infarction (NSTEMI) from other cardiac syndromes. The former is a heart attack that is characterized by a specific abnormality on a patient’s EKG tracing, referring to the fact that the reading does not include an elevated ST segment. Typically a myocardial infarction is accompanied by an elevated ST segment on an EKG when there is a complete blockage of one of the coronary arteries that feed the heart muscle; an MI that’s accompanied by a non–ST elevation may indicate a partially blocked coronary artery instead.
Designing a Low-Cost ECG Sensor and Monitor: Practical Considerations and Measures
Published in Daniel Tze Huei Lai, Rezaul Begg, Marimuthu Palaniswami, Healthcare Sensor Networks, 2016
Ahsan H. Khandoker, Brian A. Walker
The P wave is caused by atrial depolarization (contraction). The QRS complex represents ventricular depolarization, and the T wave ventricular repolarization (Gardiner 1981). Heart disease can be diagnosed on close inspection of these deflection components. For example, close RR intervals would indicate a high risk of ventricular fibrillation. Stray P waves which do not appear to be part of the cardiac cycle indicate complete heart block, which causes fainting and palpitations. Missing P waves are a strong indication of atrial fibrillation, which increases the risk of stroke. A patient who has atrial fibrillation accompanied by complete heart block would probably require a pacemaker (http://www.ecglibrary.com/). Flat or depressed ST segments could indicate coronary artery disease, which is the leading cause of death worldwide (Carson-DeWitt 2007). Sleep apnoea can be detected using the ECG (Khandoker et al. 2009) by analysing the variation in RR intervals—in particular, the RR interval variations can be analysed in the frequency domain using the Hilbert transform (Mietus et al. 2000). Interpreting abnormalities in an ECG signal is not an easy task, as it is very difficult to determine how long the abnormalities have been present. Some people are even born with such abnormalities (Cohen 2005).
Cardiac dysrhythmia management in the radiology department
Published in William H. Bush, Karl N. Krecke, Bernard F. King, Michael A. Bettmann, Radiology Life Support (Rad-LS), 2017
The electrocardiogram records the complex electrical events that occur in the heart with each cardiac cycle by assuming that the body can be regarded as a giant conductor of electrical currents. Any two points on the body surface can be connected to positive and negative ‘leads,’ with current flowing towards the positive electrode producing an upward deflection on the ECG trace. The 12-lead ECG ‘looks’ at the electrical activity in 12 different directions, any one of which could be used to evaluate the rhythm. The ‘standard limb-leads’ are conveniently selectable on most cardiac monitors by using only three leads connected to the patient. By convention, the resulting complexes are labeled the P wave, the QRS complex and the T wave. (see Fig. 6.1). Atrial depolarization produces the P wave, which is normally upright in lead II. The PR interval represents the normally slower conduction through the AV node, and should not exceed 0.2 s. The QRS complex represents ventricular depolarization, with the Q wave (the first negative deflection) not always visible. As viewed in lead II, the R wave is the next positive (upward) deflection, followed by a negative S wave. Because ventricular depolarization is a rapid event, the normal QRS is narrow and should not exceed 0.1 s. Atrial repolarization is obscured by the QRS complex. The ST segment represents the time from complete depolarization of the ventricles to the beginning of repolarization. Since no net electrical activity is occurring during this recovery phase of the cardiac cycle, the ST segment is normally flat. With ischemia or injury, the ST segment may be elevated or depressed. Ventricular repolarization results in the T wave, which is usually upright in lead II.
Context-aware system for cardiac condition monitoring and management: a survey
Published in Behaviour & Information Technology, 2022
Godwin Okechukwu Ogbuabor, Juan Carlos Augusto, Ralph Moseley, Aléchia van Wyk
‘Cardiac rehabilitation is the non-pharmacological intervention using any combination of exercise, education or psychological support to restore by their own actions, the patient's pre-disease or pre-cardiac event physical, psychological and social level of function’ (Shepherd and While 2012). It is the main aspect of secondary prevention of cardiovascular disease (Nguyen and Silva 2016), which assists patients in the recovery process and creates avenue for professionals to frequently assess the health status and offer advice on time to avoid deterioration or perhaps death. It offers training and support that assist patients return to their normal work and activities (Gay, Leijdekkers, and Barin 2009). Gimenez et al. (2006) proposed a framework aimed to develop and validate a system for integral community cardiac rehabilitation programme based on technological platform for lifestyle change supporting system. The system consists of the following characteristics: personalised cardiac rehabilitation programme, automatic support in establishing and modifying care programme, risk factor, monitoring access for the patients, intensive cardiac monitoring with automatic alarms, support self-care programmes and continuous information of the therapy results. The application acts as a personal trainer of the patient, motivating and guiding during rehabilitation. To validate the system, sensors are placed on the chest of the patient and 6 ECG signals are recorded during the exercise. Alarm warning is triggered when ECG frequency greater than the programmed value is detected, when ectopic activity is detected and when there is increment or decrement of ST segment. ST segment is the part of the ECG from the end of the QRS complex to the beginning of the T wave (Azoz et al. 2018).