what is the normal heart rate for an adult who is sitting quietly? This is a topic that many people are looking for. star-trek-voyager.net is a channel providing useful information about learning, life, digital marketing and online courses …. it will help you have an overview and solid multi-faceted knowledge . Today, star-trek-voyager.net would like to introduce to you What is a normal heart rate?. Following along are instructions in the video below:
Ill be talking about the issues and misconceptions regarding the most basic of physical physical findings. What is a normal heart rate that is the number of times per that your heart contracts pushes blood through the body and generates a pulse. Now if youre thinking everyone knows its 60 to 100 whats the big deal well you may be right that everyone knows it.
But the problem is that everyone is also wrong when talking about what constitutes a normal heart rate. There are a couple things i need to clarify first. Im referring to a normal resting heart rate.
The resting heart rate is the rate you experience when youve been sitting or lying. Still for several minutes with no significant physical activity beyond breathing at the other end of the heart rate spectrum. Does exist.
Something called the maximum predicted heart rate. Which as name implies is the fastest rate your heart can achieve during the most strenuous activity your body can perform the commonly cited equation for predicting the maximum heart rate of a person is 220 minus their age and years. Unfortunately.
While its simple to remember and even more simple to apply. Most exercise physiologists feel. Its too inaccurate and have been many attempts to better refine it.
But for today. Well be focusing on the heart rate at rest the next thing to clarify is the age of the person. Were talking about just as age impacts the maximum predictive eight.
It also impacts the resting rate. Specifically children have faster rates than adults and infants have faster. Rates than children in fact the age at which the resting heart rate is the fastest nine to ten weeks after conception when the average rate tops out at around 170 to 180 beats per minute over the next.
Several weeks. The rate slows down just a little until settling out somewhere between 120 and 160. But unless youre an obstetrician or a neonatologist you wont need to worry about fetal heart rates so for the rest of the video.
Im going to focus just on the normal resting rates in adults since there are so many adults in the world to examine and the study and since the heart rate or the pulse. Is arguably the most fundamental and basic of all physical exam. Findings you might assume that theres already a consensus about it.
In fact. Theres actually a very strong consensus among major physical exam textbooks among guides to ecg interpretation. And among instructors in medical and nursing schools.
That consensus is that the normal resting heart rate in adults is between 60 and 100 beats per minute any rate below. 60. Is considered to be a bradycardia.
Which is literally greek for slow heart any rate above.
100. Is considered to be a tachycardia. Which of course means fast heart.
This 60 to 100 consensus is so strong that have honestly never heard a member of a medical school faculty. Excluding cardiologists teach to the contrary. So whats the problem.
Well theres three of them the first problem is the evidence the largest relevant study was performed in 2007. When investigators sought to remeasure and potentially redefine the normal values for a number of aspects of resting electrocardiograms or ecg s. This included the duration of certain waveforms.
The average directionality of the electrical potential vector. Which is called the qrs axis and yes the heart rate their study subjects included 44000 adults who had been identified as having very low probability of cardiovascular disease so what did they find the median adult heart rate. Which isnt exactly the same as average heart rate was 67 with 96 of the subjects falling between 48 and 96.
There was an extremely slight gender difference and that womans rates were one to two points higher than mens these findings have a slower and slightly broader range of normal as well as a gender difference were consistent with previous smaller studies. The second problem is expert opinion in my own personal experience every cardiologist. Ive ever talked to about this issue has voiced the opinion that 60 to 100 is too high particularly the lower bound of 60 in 1992.
A survey was sent to 150 prominent cardiologists. Asking a simple question should the limits of a conventionally defined normal heart rates be changed from 60 to 102 instead 50 to 90 should it remain the same or should a different range be used 136 cardiologists responded of those 123 or 90. Agreed with a proposal of 50 to 96 voiced preference of 50 to 100 and only to prefer the traditional range and the remaining 5 had a variety of responses.
All of which were slower additional evidence of expert opinion on this issue comes from critical care medicine. In 1992. A consensus committee from the american college of chest physicians and the society of critical care medicine sought to establish uniform definitions of sepsis and the systemic inflammatory response syndrome or sirs for consistency this committee described the sirs and sepsis as states in which at least two of the following physiologic arrangements for present fever or hypothermia heart.
Rates above 90 respiratory rates above 20 and either leukocytosis or leukopenia. Although its not explicitly described in the consensus statement. Why would they have set the heart rate cutoff at 90.
If they believed the normal range to extend above this. Its logical to conclude that the committee also felt that 90 was the upper limit of normal the last problem with the traditional range of 60 to 100 is its history. Where exactly did this range come from originally well it goes back to the earliest days of electrocardiograph ii in 1928.
The new york heart association published their first edition of nomenclature and criteria for diagnosis of diseases of the heart in this book. They define something called quote. Regular sinus rhythm as a heart rhythm originating from a structure in the right atrium.
Called the sinus node from where it normally originates and is having a rate between 60 and 100 beats per minute. But 1928 was decades before any formal study was conducted into the normal distribution of heart rates in the population. So how and why could the new york heart association come up with such a range well as put by charles kaufmann.
An early member of that group.
It was for quote. The purposes of standardizing electrocardiographic nomenclature. These limits and terminology are used principally for convenience and uniformity of designation.
They do not define normality except in a gross way. However in 1943. That same new york heart association renamed regular sinus rhythm as normal sinus rhythm.
A decision. Which may have been responsible for creating this whole misconception to begin with and if that didnt feel arbitrary enough consider what a specific range of 60 to 100 was the one chosen for standardization standard electrocardiograms are printed on graph paper. Which is divided into large boxes five millimeters on a side which are then further subdivided into twenty five smaller boxes.
One millimeter on a side. Its the large boxes that were interested in the ecgs are printed out at a rate of 25 millimeters per second. Therefore.
Along the x axis. Each large box of five millimeters. Represents 1 5.
Of a second or 200 milliseconds. This has been standard convention. Since before electrocardiography was really introduced commonly into clinical practice as a consequence of this convention an interesting trick for quickly estimating heart rate.
Becomes apparent. The heart rate is equal to the number of large boxes between successive spikes known as qrs complexes divide it into 300. So if there are too large boxes between each qrs complex.
The rate is 300 divided by 2 or 150 beats per minute. If there are 4. Large boxes between each qrs complex the rate is 300 divided by 4 or 75 beats per minute.
How this becomes relevant to our 60 to 100 range is that when one is trying to determine if something is normal sinus rhythm or a tachycardia that is a rate thats too fast. If we use 100 as our cutoff one only needs see if the number of large boxes. Separating complexes is more or less than three more than three the patient has normal sinus rhythm.
Less than three the patient has a tachycardia that can be determined by inspection instantaneously. However if we use 90 as our cutoff. We would need to see if number of large boxes.
Separating complexes was more or less than three point three three a little more awkward and not quite as automatic so in essence. The decision to make the upper bound of a normal sinus rhythm. At 100.
Was because it allowed for a trivially.
Easier. Time. Interpreting.
Ecgs and even this ridiculous. Reason has been made obsolete by the use of ecg machines. Which now automatically calculate the rates with extremely high reliability.
So the traditionally taught range for normal heart rates is not supported by evidence. Its not supported by expert opinion and originates from a completely arbitrary work. And how ecgs are recorded.
Theres just one more issue to consider that is what do we even mean by the word normal when we discuss the normal heart rate are we referring to the statistical average in the general population or are we referring to the statistical average. Only in those patients who are known or suspected to have no cardiovascular disease or are we referring to a heart rate. That will minimize chance of future cardiovascular disease put more simply does normal mean typical or does normal mean healthy a 1990.
Study looked at the association between heart rates and. Mortality in. 1800.
Patients who were admitted to the hospital with a heart attack this graph here shows. The patients mortality in the first year after the heart attack as a function of their final recorded heart rates immediately prior to hospital discharge. We see that the mortality for heart rates of 50 through 89 are uniform.
But once the rate at discharge creeps above 90. Where talent he starts to climb pretty rapidly. But the danger of faster heart rates isnt limited to just patient whove had heart attacks in a study of 56000.
Patients without known heart disease the faster. The resting heart rates the increased risk of a major adverse cardiovascular event. Such as a heart attack or cardiac arrest and this trend persisted even after statistical adjustments were made to account for the presence of high blood pressure high cholesterol diabetes smoking obesity and lung disease.
So even if one believes that resting heart rates of 90 to 100 are statistically within two standard deviations of average which they probably arent they dont seem to be markers of good health. So going back to our original question. What is a normal heart rate well it depends on who your patient is and what you mean by normal.
But its probably not 60 to 100 thanks for watching my experiment in a new video style on this channel. Please let me know what you think of it in the comments keep in mind that if i continue to make some videos in this style. Now theyll be occasionally mixed in with my typical meded material and will not be displacing.
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