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Assessing and responding to sudden deterioration in the adult
Published in Nicola Neale, Joanne Sale, Developing Practical Nursing Skills, 2022
In some clinical situations, the limb leads may be placed on the torso when the limbs cannot be used. There will be a difference in the depth and height of the waves recorded if leads are placed on the torso rather than the limbs that will affect the reading of the ECG. Ask a member of the team to show you the differences in what you see. You may have observed a shift in the cardiac axis to the right, a smaller R wave in lead 1 and smaller Q waves in the inferior leads.
Conduction problems
Published in Andrew R Houghton, Making Sense of the ECG, 2019
The ECG in LBBB has an appearance as shown in Figure 9.7, with broad QRS complexes (due to the prolonged process of depolarization) and characteristic morphologies to the QRS complexes. In LBBB, the interventricular septum has to depolarize from right to left, a reversal of the normal pattern. This causes a small Q wave in lead V1 and a small R wave in lead V6 (Figure 9.8). The right ventricle is depolarized normally via the right bundle branch, causing an R wave in lead V1 and an S wave in lead V6 (Figure 9.9). Then, the left ventricle is depolarized by the right, causing an S wave in lead V1 and another R wave (called R′) in lead V6 (Figure 9.10).
Fluid Dynamics of the Aortic Valve
Published in Mano Thubrikar, The Aortic Valve, 2018
For velocity measurements a hot film probe is used. The probe consists of a conical tip where vacuum-sputtered nickel film is formed. The film is heated by an electric current to a temperature a few degrees above that of the fluid. The flowing blood carries heat away from the film at a rate dependent upon the velocity of the blood, thereby dropping the temperature of the probe. To maintain the constant temperature, the current is supplied to the probe by varying the voltage. Hence the variation in voltage directly represents velocity of the blood flow. To measure velocity in the ascending aorta, a probe travel assembly is fitted around the aorta. Several pulses are recorded with the probe in one position before it is advanced to another position. A standard electrocardiogram is recorded and R wave is used as a reference point to synthesize the velocity profile. For example, at the time of R wave, the magnitudes of velocities in all the probe positions are grouped together to obtain a single velocity profile. This is repeated at various predefined intervals from R wave so as to obtain the profiles throughout systole.
Meta-analysis of clinical outcomes in cardiac resynchronisation therapy: his bundle pacing vs biventricular pacing
Published in Expert Review of Medical Devices, 2023
Antonio da Silva Menezes Junior, Maria Gabriella Zordan Melo, Lara Pedriel Barreto
However, recent research has compared HBP with BiV to assess the potential benefits of each as CRT. To achieve the best possible clinical results, physiological stimulation uses both left bundle branch pacing (LBBP) and His-Purkinje system (HBP) stimulation, which are considered new-generation methods that can mimic physiological rhythm or fully restore atrioventricular activity. LBBP stimulates the conduction system of the heart and deep septal myocardium, resulting in a lower rhythm capture threshold and an R-wave amplitude greater than that of HBP [16–18]. The His-Purkinje conduction system typically causes genuine cardiac resynchronization. Patients with right ventricular septal pacing reportedly have worse ventricular mechanical synchronization characteristics than those with HBP [19,20].
The streamlined allostatic load index is associated with perceived stress in life – findings from the MIDUS study
Published in Stress, 2021
Cardiovascular reactivity was assessed in the morning after a light breakfast with no caffeinated beverages via continuous measurement of a 3-lead electrocardiogram (ECG). ECG electrodes were placed on the left and right collarbones, and in the left lower quadrant of the abdomen. Beat-to-beat ECG waveforms were then analyzed to calculate heart rate variability (HRV). HRV reflects activity of the parasympathetic nervous system with higher values usually indicating a better health status. HRV is operationalized as variability in the series of intervals between consecutive R waves. Analog beat-to-beat ECG signals were digitized at a sampling rate of 500 Hz by a National Instruments A/D board and passed to a microcomputer for collection. ECG waveforms were submitted to an R-wave detection routine implemented by a proprietary event detection software (Graphical Marking, Delano McFarlane), resulting in an RR interval series. Research staff visually reviewed all ECG waveforms to correct interactively any software errors in identifying normal R waves. The resulting series of normal RR intervals were used to calculate HRV. Time-domain index of RR interval variability was calculated as root mean squared successive differences (RMSSD).
The electrocardiographic changes associated with hypothermia: the Osborn wave
Published in Acta Cardiologica, 2020
Francesca Cortese, Alessandra Paglia, Rocco Contuzzi, Andrea Andriani, Luigi Truncellito, Giacinto Calculli
It consists of an electrocardiographic deflection which is manifested as a late delta wave or as a small r ’wave following the QRS. It is the manifestation on the surface ECG of the electric gradient between a more prominent spike and dome action potential of epicardial cells than that of endocardial cells, an effect that is believed to be linked to a slowing down of the kinetics of activation of K + channels Ito compared to calcium channels, associated with low temperature. This wave is not specific for hypothermia but can also occur in other clinical conditions such as subarachnoid haemorrhage, myocardial ischaemia, acidosis, in the presence of hypercalcemia, early repolarization and even in normal subjects. Its amplitude also tends to increase in conjunction with the reduction in body temperature. The bradyarrhythmias and conduction disorders associated with hypothermia cease spontaneously with an increase in body temperature, so the use of beta stimulating drugs and the insertion of transvenous pacemakers, the latter for the mechanical irritation effect on the endocardium, should be considered with caution due to the high risk of inducing ventricular tachyarrhythmias and ventricular fibrillation.