Cardiol, A., (2018). pediag > Blog > Uncategorized > how could a fetal arrhythmia affect fetal oxygenation? How common is it? We also follow baby closely as well, to make sure their heart rhythm is slowed to a safe rate. 33.4), renal artery and vein (Fig. What is the normal fetal heart rate? Fetal arrhythmia is a term that refers to any abnormality in the heart rate of your baby. Detailed analysis of the type of arrhythmia in utero is possible using M-mode and Doppler echocardiography. how could a fetal arrhythmia affect fetal oxygenation? Pregnancy outcomes in patients with autoimmune diseases and anti-Ro/SSA antibodies. 4. The baseline rate is interpreted as changed if the alteration persists for more than 15 minutes. compte fortnite switch gratuit; luke ducharme actor older; regence claims address; excel android video; property guys stephenville, nl; ucf college of medicine acceptance rate Late decelerations are associated with uteroplacental insufficiency and are provoked by uterine contractions. A scalp pH of less than 7.20 is considered abnormal and generally is an indication for intervention, immediate delivery, or both.12 A pH less than 7.20 should also be assumed in the absence of an acceleration following fetal scalp stimulation when fetal scalp pH sampling is not available. Unless there are signs that the fetus is in trouble, pre-term delivery or Cesarean section is not necessary. The fetal membranes must be ruptured, and the cervix must be at least partially dilated before the electrode may be placed on the fetal scalp. Healthline Media does not provide medical advice, diagnosis, or treatment. how could a fetal arrhythmia affect fetal oxygenation? Figure 33.5: Pulsed Doppler of renal artery and vein in a fetus with normal sinus rhythm. Consuming turmeric in pregnancy is a debated subject. The characteristics of first-, second-, or third-degree (complete) heart block are presented in Table 33.1. Atrial contractions (A) are identified by the start of the A-wave in the renal vein Doppler waveform and ventricular contractions (V) by the renal artery flow. This is known as fetal arrhythmia. Up to 40% of congenital AV heart block (CAVB) cases (Fig. The presence of a saltatory pattern, especially when paired with decelerations, should warn the physician to look for and try to correct possible causes of acute hypoxia and to be alert for signs that the hypoxia is progressing to acidosis.21 Although it is a nonreassuring pattern, the saltatory pattern is usually not an indication for immediate delivery.19. Variable decelerations associated with a nonreassuring pattern, Late decelerations with preserved beat-to-beat variability, Persistent late decelerations with loss of beat-to-beat variability, Nonreassuring variable decelerations associated with loss of beat-to-beat variability, Confirmed loss of beat-to-beat variability not associated with fetal quiescence, medications or severe prematurity, Administer oxygen through a tight-fitting face mask, Change maternal position (lateral or knee-chest), Administer fluid bolus (lactated Ringer's solution), Perform a vaginal examination and fetal scalp stimulation, When possible, determine and correct the cause of the pattern, Consider tocolysis (for uterine tetany or hyperstimulation), Consider amnioinfusion (for variable decelerations), Determine whether operative intervention is warranted and, if so, how urgently it is needed, A blunt acceleration or overshoot after severe deceleration, Late decelerations or late return to baseline (. (2009). Another type of arrythmia we treat quite often is supraventricular tachycardia, or SVT. Of all tachyarrhythmias, atrial flutter and SVT heart rate between 220 and 300 beats per minute are the most common types you may see. Fetal arrhythmias are relatively common and account for 1020% of referrals to fetal cardiology. Pulsed Doppler echocardiographic assessment of the AV time interval is indirectly derived from flow measurements, which are influenced by loading condition, intrinsic myocardial properties, heart rate, and propagation speed (8). Chemoreceptors located in the aortic and carotid bodies respond to hypoxia, excess carbon dioxide and acidosis, producing tachycardia and hypertension.15 The FHR is under constant and minute adjustment in response to the constant changes in the fetal environment and external stimuli. In some cases, however, we will monitor your baby and advise mom to reduce caffeine and stress. They are usually associated with fetal movement, vaginal examinations, uterine contractions, umbilical vein compression, fetal scalp stimulation or even external acoustic stimulation.15 The presence of accelerations is considered a reassuring sign of fetal well-being. Quis autem velum iure reprehe nderit. It may also be performed using an external transducer, which is placed on the maternal abdomen and held in place by an elastic belt or girdle. This article explains how doctors diagnose a fetal arrhythmia, the different types, possible causes, and treatments. Note the green coloration of the right ventricle (RV) in fetus B (arrows), indicating right ventricular dysfunction. (2012). 4. Develop a plan, in the context of the clinical scenario, according to interpretation of the FHR. The prenatal diagnosis of cardiac rhythm abnormalities has been made possible with advancements in ultrasound imaging. Fetal arrhythmias may not always be caused by a structural heart defect, though. This chapter will review the diagnostic modalities currently available for the assessment of fetal rhythm abnormalities and the various types of fetal arrhythmias, as well as their impact on fetal and neonatal outcome and their management. PVCs are also benign in the majority of cases. These patients often require open heart surgery to repair both problems. Atrioventricular block during fetal life. CAVB occurs in about 1 in 11,000 to 1 in 22,000 live births in the general population and in 1% to 2% of live births in pregnancies with anti-SSA/Ro antibodies, with a recurrence risk of 14% to 17% in these pregnancies (2023). How Viagra became a new 'tool' for young men, Ankylosing Spondylitis Pain: Fact or Fiction, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6531664/, https://www.karger.com/Article/FullText/519911, https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5963229/, https://www.heart.org/en/health-topics/congenital-heart-defects/symptoms--diagnosis-of-congenital-heart-defects/fetal-echocardiogram-test, https://clinmedjournals.org/articles/ogcr/obstetrics-and-gynaecology-cases-reviews-ogcr-6-146.php, https://www.revespcardiol.org/en-fetal-arrhythmias-diagnosis-treatment-perinatal-articulo-S1885585715002352, https://imj.ie/uncomplicated-fetal-tachycardia-in-labour-dilemmas-and-uncertainties/, https://www.ahajournals.org/doi/10.1161/JAHA.119.013436, https://www.nhlbi.nih.gov/health/arrhythmias, https://www.aerjournal.com/articles/pharmacological-therapy-tachyarrhythmias-during-pregnancy. The FHR is controlled by the autonomic nervous system. As antibody levels rise, the baby is at an increased risk for complete heart block. 33.2) and steering of the M-mode beam, which is available in newer ultrasound equipment, allow for enhanced performance. It can be overwhelming researching them on your own ask your doctor to explain your babys to you so you understand whats going on and what part of the heart is affected. Arrhythmias are discovered in about 1% of fetuses. Any medical information published on this website is not intended as a substitute for informed medical advice and you should not take any action before consulting with a healthcare professional. All rights reserved. If things are stable or improve on their own, no further treatment may be necessary. Fetal Arrhythmia/Dysrhythmia A healthy fetus has a heartbeat of 120 to 160 beats per minute, beating at a regular rhythm. By adjusting gain and velocity of color and pulsed Doppler ultrasound, cardiac tissue Doppler imaging can be obtained with standard ultrasound equipment (9). Brucato A, et al. Blocked premature beats are typically benign and tend to resolve with increased fetal activity. However, on rare occasions, irregular heart rhythm can lead to death. The monitor calculates and records the FHR on a continuous strip of paper. You may notice its faster than your own. In some cases, healthcare providers may not be able to pinpoint the source, especially if the abnormal rhythm is transient. Copyright 2023 American Academy of Family Physicians. Here, learn about the structure of the heart, what each part does, and how it works to support the body. Doctors prescribe medication to treat fetal arrhythmias. Compiled using information from the following sources: 1. A scalp pH less than 7.25 but greater than 7.20 is considered suspicious or borderline. The time interval between consecutive atrial impulses is relatively constant in AV block as opposed to a shortened atrial impulse interval on every second or third beat in bigeminy or trigeminy, respectively. When it occurs earlier in pregnancy, it may be the result of other problems and may lead to heart failure and even fetal death. Stephenson, E. (2010, March 19). Of these arrhythmias, 10% are considered potential sources of morbidity. The Centers for Disease Control and Prevention (CDC) report that around 1 percent of babies (40,000) are born with congenital heart defects each year in the United States. What is a fetal arrhythmia and how is it treated? Limitations of this technology include its lack of availability in many centers and the need for a magnetically shielded room (10, 11). In these cases, heart block is related to a structural issue, not a signaling problem, and cannot be treated with steroids. Irregular fetal cardiac rhythm is the leading cause for referrals to fetal echocardiography centers for rhythm disturbances, and the vast majority of those are benign atrial ectopic beats. Any decrease in uterine blood flow or placental dysfunction can cause late decelerations. Fetal arrhythmia refers to an abnormal fetal heartbeat or rhythm. And transient arrhythmias those that come and go are more common than sustained arrhythmias, ones that are present always or more often than not. Fetal tachycardia is a faster heart rate than expected. In most cases, your newborn will receive medications to regulate the heartbeat. This arrhythmia happens when the fetus has extra heartbeats, or ectopic beats, that originate in the atria (PACs) or the ventricles (PVCs). Determine whether accelerations or decelerations from the baseline occur. Tachycardia is considered mild when the heart rate is 160 to 180 bpm and severe when greater than 180 bpm. Bravo-Valenzuela NJ, et al. M-mode (motion-mode) echocardiography is obtained by recording ultrasound beam reflections in relation to depth from the transducer and time. In some cases of severe bradycardia, medication alone is not effective and a pacemaker may need to be implanted. To be classified as sustained bradycardia, your babys heart rate must remain low for 10 minutes or more when monitored. live music port clinton ohio; colleges that allow freshmen to live off campus FHR, fetal heart rate. The M-mode cursor line intersects the right atrium (RA) and left ventricle (LV). If your doctor suspects your baby has an arrhythmia, you may be sent for more detailed imaging called a fetal echocardiogram. Our website services, content, and products are for informational purposes only. Uterine tachsystole B. Maternal hypotension C. Prolapsed cord An arrhythmia is a term used to describe any abnormal or irregular heartbeat. PACs are due to atrial ectopic beats (atrial ectopy), which occur most commonly in the late second trimester of pregnancy through term and are usually benign. With a complete heart block, for example, doctors may treat it by giving you steroids or medications like hydroxychloroquine. In animal studies, administration of amiodarone to rabbits, rats, and mice during organogenesis resulted in embryo-fetal toxicity at doses less than the maximum recommended human maintenance . (2015). Babies can be diagnosed with arrhythmia before they are born. However, there may be questions about the condition that warrants further investigation. If the PACs are nonconducted, this can cause short intermittent slowing of the heart beat while the heart recovers; this may sound like an intermittent slow heart rate. Nonreassuring variable decelerations associated with the loss of beat-to-beat variability correlate substantially with fetal acidosis4 and therefore represent an ominous pattern. Oyen N, et al. The FHR recordings may be interpreted as reassuring, nonreassuring or ominous, according to the pattern of the tracing. This test lets your doctor see your unborn childs heart. SVT typically resolves before or after birth, either by itself or with medical therapy. 8. The mechanical PR interval can also be evaluated by pulsed Doppler (see later in this chapter) (6). A person viewing it online may make one printout of the material and may use that printout only for his or her personal, non-commercial reference. These can include tachycardia-an increased heart rate-or bradycardia, which is a slowed heartbeat. Fetal arrhythmia is caused by abnormalities or interruptions in the hearts electrical system. For some babies, however, fetal arrhythmia may require treatment. Nonreassuring patterns such as fetal tachycardia, bradycardia and late decelerations with good short-term variability require intervention to rule out fetal acidosis. De Carolis S, et al. 3. When a pregnant person takes medication, it passes through the placenta to the unborn baby. A pattern of persistent late decelerations is nonreassuring, and further evaluation of the fetal pH is indicated.16 Persistent late decelerations associated with decreased beat-to-beat variability is an ominous pattern19 (Figure 7). An acceleration pattern preceding or following a variable deceleration (the shoulders of the deceleration) is seen only when the fetus is not hypoxic.15 Accelerations are the basis for the nonstress test (NST). Additional monitoring allows your doctor to keep an eye on your baby and develop a treatment plan for during or after pregnancy, if necessary. This frittata is high in protein and rich in essential nutrients your body needs to support a growing baby. Differentiating this type of bradycardia from AV heart block is critical given a divergent prognosis. Figure 33.4: Pulsed Doppler of pulmonary artery and vein in a fetus with normal sinus rhythm. Immediate appointments are often available. A healthy fetal heart rate ranges between 110 and 160 beats per minute. Data and statistics on congenital heart defects. Fetal tachycardia is defined as a baseline heart rate greater than 160 bpm and is considered a nonreassuring pattern (Figure 3). Your doctor may discover this anomaly when doing a routine ultrasound or listening to your babys heart with a Doppler device. You will most likely be able to hold your baby after delivery. The transducer uses Doppler ultrasound to detect fetal heart motion and is connected to an FHR monitor. Not all fetal arrhythmias require special treatment. When a babys heart rate is slower or faster than this or has some other issue, like skipping beats it may indicate theres an issue, like a heart defect, that needs more monitoring. Sometimes, if your baby is close to term, we will go ahead and deliver. Arrhythmia most often refers to an irregular heartbeat, while dysrhythmia represents all types of abnormal heartbeats: the heartbeat can be too fast (tachycardia) or too slow (bradycardia). Keywords . Baroreceptors influence the FHR through the vagus nerve in response to change in fetal blood pressure. PCs is the most common type of fetal arrhythmia. Zaidi, A., & Ro, P. (n.d.). A heart rate that is faster or slower than this may indicate that there is an issue that needs further attention. We avoid using tertiary references. Atrial tachycardia (AT) occurs when the hearts upper chambers, the atria, beat too quickly. Classification of cardiac arrhythmias in the neonate, child, and adult is aided by established criteria primarily by ECG findings. from the fetal blood so helping to "repay" a fetal oxygen debt.1 The causes of fetal hypoxia and therefore acidosis can be divided into maternal, placen-tal, or fetal. As a result, the fetus can go into heart failure. 2005-2023 Healthline Media a Red Ventures Company. Irregular fetal cardiac rhythm is the leading cause for referrals to fetal echocardiography centers for rhythm disturbances, and the vast majority of those are benign atrial ectopic beats. The normal FHR range is between 120 and 160 beats per minute (bpm). The presence of at least two accelerations, each lasting for 15 or more seconds above baseline and peaking at 15 or more bpm, in a 20-minute period is considered a reactive NST. where do you file a complaint against a hospital; failure to pay full time and attention va code; bones angela and hodgins in jail; mirabella svadobny salon dubnica nad vahom The most common types you may encounter include the following: Premature contractions are the most common type of arrhythmia thats found in the second and third trimesters of pregnancy. We are currently involved in a research study investigating home monitoring, home ultrasound and whether or not early administration of steroids is effective. Postdate gestation, preeclampsia, chronic hypertension and diabetes mellitus are among the causes of placental dysfunction. Fetal magnetocardiography (fMCG) is not yet widely available. It's typically diagnosed after an individual develops multiple pregnancies at once. They take various factors into account before choosing treatments, including maternal health and the severity of the condition. Evaluate recordingis it continuous and adequate for interpretation? The most common cause of heart block is when mom is carrying antibodies associated with lupus or Sjogrens syndrome (autoimmune conditions). Cardiovascular health: Insomnia linked to greater risk of heart attack. A more recent article on intrapartum fetal monitoring is available. 33.12) occur in fetuses with congenital cardiac malformations, especially left atrial isomerism (heterotaxy) (see Chapter 30) or congenitally corrected transposition of the great arteries (see Chapter 28). Some studies have stated that maternal oxygen supplementation can alleviate abnormal patterns of fetal heart rate (FHR) but does not improve fetal acid-base status . No therapy is necessary in the majority of cases with irregular cardiac rhythm when the cause is atrial or with ventricular ectopic beats as most resolve spontaneously. how could a fetal arrhythmia affect fetal oxygenation?aripartnerconnect login 03/06/2022 / jobs at stafford leys school / en winchester' movie true story / por / jobs at stafford leys school / en winchester' movie true story / por Other babies may need regular monitoring and treatment, especially if their arrhythmia affects blood flow. In the United States, an estimated 700 infant deaths per year are associated with intrauterine hypoxia and birth asphyxia.5 Another benefit of EFM includes closer assessment of high-risk mothers. Genetic syndromes associated with congenital heart disease. Last medically reviewed on October 29, 2021. Variable decelerations may be classified according to their depth and duration as mild, when the depth is above 80 bpm and the duration is less than 30 seconds; moderate, when the depth is between 70 and 80 bpm and the duration is between 30 and 60 seconds; and severe, when the depth is below 70 bpm and the duration is longer than 60 seconds.4,11,24 Variable decelerations are generally associated with a favorable outcome.25 However, a persistent variable deceleration pattern, if not corrected, may lead to acidosis and fetal distress24 and therefore is nonreassuring. (n.d.). Causes of fetal bradycardia include sinus bradycardia, blocked atrial bigeminy/trigeminy, and high-degree AV block (17). In the unusual circumstance that the arrhythmia is more severe, the baby may be born with a heart irregularity that is managed throughout his or her life. on georgia law on drug testing newborns 2019; whole health recovery . DiLeo, G. (2002). Introduction. Identify pattern of uterine contractions, including regularity, rate, intensity, duration and baseline tone between contractions. Untreated underlying arrhythmias, including ventricular arrhythmias, during pregnancy pose a risk to the mother and fetus (see Clinical Considerations). Post comments: direct characterization of clarisse fahrenheit 451 direct characterization of clarisse fahrenheit 451 Most patients who undergo internal fetal monitoring during labor accept monitoring as a positive experience.6. The sinus node is in the right atrium, and the AV node is in the middle of the heart, between the atria and ventricles. The trigeminy is also clearly seen in the umbilical artery pulsed Doppler spectrum (B). More information on optimizing tissue Doppler display is presented in Chapter 14. Maternal caffeine consumption and pregnancy outcomes: a narrative review with implications for advice to mothers and mothers-to-be. In most cases, the cause of the disruption is unknown, but it can result from an electrolyte imbalance, inflammation or medication. Atrial contractions (A) are identified by the retrograde A-wave in the SVC and ventricular contractions (V) by the aortic flow. Heart block can quickly progress into complete heart block, a more dangerous condition, where there is no communication at all between the sinus and AV node. Non-conducted PACs result in bradycardia. Two premature atrial contractions are shown (arrows) followed by two premature ventricular contractions (asterisks). Steroids can sometimes be used to slow the progression to complete heart block when antibodies are the cause, but the results are not conclusive. Prematurity, maternal anxiety and maternal fever may increase the baseline rate, while fetal maturity decreases the baseline rate. A fetal arrhythmia may be diagnosed when a developing babys heart rate falls outside the normal range of 120 to 180 beats per minute (BPM). The anxious parents Guide to Pregnancy (p. 108). While most fetal arrhythmias are benign, certain cases may require medical intervention. When a doctor suspects an irregular fetal heart rate, they may order a fetal echocardiogram. Prematurity decreases variability16; therefore, there is little rate fluctuation before 28 weeks. Ko JM. Fetal tachycardia refers to a heart rate faster than 180 bpm. Get the latest on vaccine information, in-person appointments, video visits and more. A premature atrial contraction is an extra beat in the hearts upper chambers. Healthline has strict sourcing guidelines and relies on peer-reviewed studies, academic research institutions, and medical associations. These antibodies can cause inflammation in the fetal heart, blocking the AV nodes ability to react to the sinus node. The baseline rate is interpreted as changed if the alteration persists for more than 15 minutes. Significant progress is under way, and future technologic improvements in this field will undoubtedly facilitate the use of fetal ECG in the classification of arrhythmias. What is the latest research on the form of cancer Jimmy Carter has? Fetal cardiac arrhythmia detection and in utero therapy. The FHR is under constant variation from the baseline (Figure 1). The atrial contractions are shown by straight arrows and occur at a regular and normal rate. PACs can be either conducted or blocked, resulting in an irregular rhythm or a short pause, respectively. These extra beats are caused by early (premature) contractions of the hearts upper (atrial) or lower (ventricle) chambers. Results in this range must also be interpreted in light of the FHR pattern and the progress of labor, and generally should be repeated after 15 to 30 minutes. Regardless of the depth of the deceleration, all late decelerations are considered potentially ominous. Figure 33.3: Pulsed Doppler of left ventricular (LV) inflow (mitral valve) and outflow (aortic valve) in a fetus with normal sinus rhythm. There are two types of fetal arrhythmias: Fetal arrhythmia is rare. Table 3 lists examples of nonreassuring and ominous patterns. The true sinusoidal pattern is rare but ominous and is associated with high rates of fetal morbidity and mortality.24 It is a regular, smooth, undulating form typical of a sine wave that occurs with a frequency of two to five cycles per minute and an amplitude range of five to 15 bpm. when did the mixing bowl close Menu Menu. 33.3), pulmonary artery and vein (Fig. Clinically, loss of beat-to-beat variability is more significant than loss of long-term variability and may be ominous.18 Decreased or absent variability should generally be confirmed by fetal scalp electrode monitoring when possible. Furthermore, poor signal quality and suboptimal fetal position are often encountered, which limits the application of M-mode. 1. If the PACs are conducted, the ventricles have extra contractions, and this sounds like intermittent extra heart beats. Auscultation of the fetal heart rate (FHR) is performed by external or internal means. With PCs, your baby has extra heartbeats that can either originate in the atria (premature atrial contractions or PACs) or the ventricles (PVCs). With SVT, we are usually able to stop or slow the rhythm before the baby is born, providing proper care for both mom and baby. The bigeminy is also clearly seen in the umbilical artery pulsed Doppler spectrum (B). coconut milk smells like sulfur what happened to tom from choccywoccydoodah midland women's soccer roster It is possible that high levels of caffeine consumption may cause heartbeat irregularities, but currently, only case studies have been performed. This pregnancy-friendly spin on traditional chili is packed with the nutrients your body needs when you're expecting. Since such technology is not technically feasible in the fetus, a more practical approach to the classification of fetal arrhythmias is used, which relies on ultrasound-derived technologies, such as M-mode, pulsed Doppler, and tissue Doppler. Debra Rose Wilson, Ph.D., MSN, R.N., IBCLC, AHN-BC, CHT, problems with the hearts electrical signals, structural abnormalities within the heart, restricted blood flow to the heart, or ischemia, is taking sympathomimetic medications such as terbutaline, ion channel dysfunction, such as Long-QT syndrome, medications taken by the pregnant person, including, rare metabolic disorders, such as Pompes disease. If your doctor suspects fetal arrythmia, you need to consult a fetal cardiologist immediately. Another 0.5% will develop supraventricular tachycardia. In both blocked premature beats and AV heart block, the atrial rate is higher than the ventricular rate. However, there are common causes, including: There are many types of fetal arrhythmias. If treatment is still needed for recurrent SVT around the age of 8 or 9, a catherization procedure can usually correct it permanently. metea valley high school map; horse barn kits near hamburg; habit breaking appliance for tongue thrusting; kontoor brands nottingham address; senate bill 25 pennsylvania 33.6). There is a remote chance that fetal death may occur while in the womb or during delivery. An arrhythmia is an irregular heart rate too fast, too slow, or otherwise outside the norm. Treatment of Fetal and Neonatal Arrhythmias. This pattern is most often seen during the second stage of labor. All Rights Reserved. This content is owned by the AAFP. Can diet help improve depression symptoms? Tissue Doppler imaging is a relatively new technique that allows direct analysis of segmental wall motion (myocardial velocities) in any area of the fetal heart during the same cardiac cycle (7). Maintaining fetal oxygenation to preserve fetal viability and sustain fetal growth throughout pregnancy involves the complex interrelationship between the fetus, the placenta, and the pregnant woman. The rhythm of the heart is controlled by the sinus node (known as the pacemaker of the heart) and the atrioventricular node (AV node). Figure 33.9: M-mode recording of a fetus with conducted premature atrial contractions. The normal heart rate for a fetus is anywhere between 120 and 160 beats per minute. Document in detail interpretation of FHR, clinical conclusion and plan of management. Around 30 percent of sustained bradycardia cases will resolve without treatment before delivery. According to an article in the Indian Pacing and Electrophysiology Journal, the normal fetal heart rate ranges between 110 and 160. how could a fetal arrhythmia affect fetal oxygenation? But what does this actually mean? However, it can provide a more accurate picture of a fetus heart than fECG. A very fast heart rate may be caused by abnormal firing of the nerves that are responsible for the heartbeat. A comprehensive, integrated, academic health system with The Warren Alpert Medical School of Brown University, Lifespan's present partners also include Rhode Island Hospital's pediatric division, Hasbro Children's Hospital; Bradley Hospital; Newport Hospital; Gateway Healthcare; Lifespan Physician Group; and Coastal Medical. Also, arrhythmia may, at some point in development, be normal.