Are Common Heart Skip Palpitations Dangerous?: Premature Ventricular and Atrial Contractions (PVCs and PACs)
pvc ventricular - click on the image below for more information.
pvc ventricular
INTRODUCTION: Skipped heartbeats occur in most, if not 100% of the general population, at some point during their lives. Some medical sources state that about half of us experience them on a relatively frequent basis. For some people however, these heart palpitations called "Premature Ventricular Contractions" and "Premature Atrial Contractions" (PVCs and PACs), occur at a frequency or forcefulness, that can be concerning to them and that can result in chronic anxiety and/or panic att
Are Common Heart Skip Palpitations Dangerous?: Premature Ventricular and Atrial Contractions (PVCs and PACs)
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Photoplethysmograph
Article by jekky
(721, 'Sites for measuring PPG br While pulse oximeters are a commonly used medical device the PPG derived from them is rarely displayed and is nominally only processed to determine heart rate PPGs can be obtained from transmissive absorption as at the finger tip or reflective as on the forehead br In outpatient setting pulse oximeters are commonly worn on the finger and ear However in cases of shock hypothermia etc blood flow to the periphery can be reduced resulting in a PPG without a discernible cardiac pulse In this case a PPG can be obtained from a pulse oximeter on the head with the most common sites being the ear nasal septum and forehead br PPGs can also be obtained from the vagina and esophagus br Uses br Premature Ventricular Contraction PVC can be seen in the PPG just as in the EKG and the Blood Pressure BP br Venous pulsations can be clearly seen in this PPG br Monitoring Heart Rate and Cardiac Cycle br Because the skin is so richly perfused it is relatively easy to detect the pulsatile component of the cardiac cycle The DC component of the signal is attributable to the bulk absorption of the skin tissue while the AC component is directly attributable to variation in blood volume in the skin caused by the pressure pulse of the cardiac cycle br The height of AC component of the photoplethysmogram is proportional to the pulse pressure the difference between the systolic and diastolic pressure in the arteries As seen in the figure showing Premature Ventricular Contractions PVCs the PPG pulse for the cardiac cycle with the PVC results in lower amplitude blood pressure and a PPG Ventricular Tachycardia and Ventricular Fibrillation can also be detected br Monitoring Respiration br The effects of Sodium Nitroprusside Nipride a peripheral vasodilator on the finger PPG of a sedated subject As expected the PPG amplitude increases after infusion and additionally the Respiratory Induced Variation RIV becomes enhanced br Respiration affects the cardiac cycle by varying the intrapleural pressure the pressure between the thoracic wall and the lungs Since the heart resides in the thoracic cavity between the lungs the partial pressure of inhaling and exhaling greatly influence the pressure on the vena cava and the filling of the right atrium This effect is often referred to as normal sinus arrhythmia br During inspiration intrapleural pressure decreases by up to 4 mm Hg which distends the right atrium allowing for faster filling from the vena cava increasing ventricular preload and increasing the stroke volume Conversely during expiration the heart is compressed decreasing cardiac efficiency and reducing stroke volume However the overall net effect of respiration is to act as pump for the cardiovascular system When the frequency and depth of respiration increases the venous return increases leading to increased cardiac output Shelley et al 2006 br Monitoring Depth of Anesthesia br Effects of an incision on a subject under general anesthesia on the photoplethysmograph PPG and blood pressure BP br Anesthesiologist must often judge subjectively whether a patient is sufficiently anesthetized for surgery As seen in the figure if a patient is not sufficiently anesthetized the sympathetic nervous system response to an incision can generate an immediate response in the amplitude of the PPG br Monitoring Hypo and Hyper volemia br Shamir Eidelman et al studied the interaction between inspiration and removal of 10 of a patient blood volume for blood banking before surgery Shamir Eidelman et al 1999 They found that blood loss could be detected both from the photoplethysmogram from a pulse oximeter and an arterial catheter Patients showed a decrease in the cardiac pulse amplitude caused by reduced cardiac preload during exhalation when the heart is being compressed br References br M Shamir L A Eidelman Y Floman L Kaplan and R Pi zov Pulse Oximetry Plethysmographic Waveform During Changes in Blood Volume Br J Anaesth vol 82 pp 178 181 1999 br K Shelley and S Shelley Pulse Oximeter Waveform Photoelectric Plethysmography in Clinical Monitoring Carol Lake R Hines and C Blitt Eds W B Saunders Company 2001 pp 420 428 br K H Shelley D H Jablonka A A Awad R G Stout H Rezkanna and D G Silverman What Is the Best Site for Measuring the Effect of Ventilation on the Pulse Oximeter Waveform Anesth Analg vol 103 pp 372 377 2006 br A T Reisner P A Shaltis D McCombie and H H Asada Utility of the Photoplethysmogram in Circulatory Monitoring Anesthesiology vol 108 pp 950 958 2008 br External links br A student project building a device for collecting PPGs br See also br Hemodynamics br Categories Cardiology Medical tests')
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