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Why is the first phase of the pulse from a pacemaker cathodic?
How Does Homeostasis Control Heart Rate?
Homeostasis regulates the heart rate and all of its internal functions to maintain equilibrium. According to Biology Online, homeostasis uses a negative and positive feedback system to keep the human body running efficiently.
The portion of the brain stem that controls the heart rate is the medulla. The medulla transmits chemical messages and nerve impulses through the medulla pyramids. According to DHearts.com, the medulla pyramids are where all communication for the muscles, organs, and other areas of the body take place. During exercise and periods of high activity, the muscles in your body send messages through the brain stem to the medulla. The medulla then releases two hormones, epinephrine and norepinephrine, which travel through the brain stem to the heart. Once those two hormones reach the sinus node, they stimulate electrical impulses in the heart muscles and cause the heart muscle to contract faster.
When you stop exercising or decrease your level of activity, the muscles in the body send another message to the medulla to release acetylcholine.This hormone slows down the contractions of the heart, and allows the heart to rest by reducing the heart rate.
According to Biology Online, each beat of the heart pumps blood and oxygen to the muscles and organs of the body, so they can function properly. While oxygen is being delivered throughout the body, carbon dioxide is being removed to keep all of the cells, organs, muscles, and blood clean and healthy.
Why is my heart rate jumping up and down?
In adults, a typical resting heart rate is 60–80 beats per minute (bpm). This rate can rise or fall due to structural or electrical disorders of the heart. Changes may also be due to certain behavioral or environmental factors.
An irregular heart rhythm can cause the heart rate to jump between high and low in a condition called arrhythmia, or dysrhythmia. This can be alarming, but it does not always result in severe health complications.
Nonetheless, if a person suspects anomalies in the rhythm of their heart rate, they should contact a doctor for a diagnosis.
This article will examine several possible causes of a heart rate that is jumping up and down, beginning with some structural and electrical disorders of the heart. It will also detail some possible behavioral and environmental causes, such as stress and dehydration, and explain when a person should contact a doctor.
Tachycardia means that an adult’s heart rate is over 100 bpm.
There are several types of tachycardia. The sections below will look at some of these in more detail.
In sinus tachycardia, the heart rate increases but continues to beat properly in the normal rhythm.
Sinus tachycardia occurs when the heart rate increases due to expected reasons, such as during exercise, if a person is feeling anxious, or during periods of dehydration.
Inappropriate sinus tachycardia, which is rare, occurs when the heart rate increases for no apparent reason. It could be the result of a nerve signaling problem in the heart.
Supraventricular tachycardia occurs when there is a disruption to the electrical signal.
This disruption prevents the heartbeat from originating in the sinoatrial node (which creates sinus rhythm) and instead causes it to originate in another part of the top chamber of the heart.
The word supraventricular means that the arrhythmia originates from the top chamber of the heart. The word tachycardia means that it results in a heartbeat that is higher than 100 bpm.
Supraventricular tachycardia may cause symptoms such as:
However, there may be no symptoms at all.
It is rare that supraventricular tachycardia results in sudden death, but this can happen if the heart rate gets too fast.
According to one 2020 study , a person with supraventricular tachycardia who wishes to slow down their heart rate can try several types of Valsalva maneuver.
To try the most well-known type of Valsalva maneuver, a person should bear down, as if they were passing a bowel movement, for 10–15 seconds.
However, if this method does not work, they could try the following other types:
- immersing themselves or just their face in cold water
- blowing on their thumb (in children) or into an empty syringe
Atrial fibrillation (A-fib) results from complex waves in the upper and lower chambers of the heart causing an irregular heartbeat. It is a common arrhythmia.
According to some studies, females with A-fib are more likely to experience symptoms than males.
The following signs will help your doctor diagnose a pacemaker disorder:
- A pulse that does not go up during exercise
- A pulse that varies greatly even if your activity level has not changed
- A slow pulse, especially if it is an irregular one
Your doctor will usually base his or her diagnosis on your symptoms and on the results of an electrocardiogram. He or she may monitor your heart rhythm using a Holter monitor, which allows your heart rate to be recorded continuously over a 24-hour period.
Abnormal Heart Rhythm (Bradycardia)
What is abnormal heart rhythm?
There are many kinds of abnormal heart rhythms, which are collectively known as arrhythmias. One of the most common is abnormally slow heartbeats, a condition known as bradycardia. For most people, a normal resting heart rate is considered to be between 60 to 100 beats a minute anything less than this may be considered bradycardia.
It is important to note that a slow heart rate can sometimes be normal, and even a sign of good physical fitness. Healthy young adults and athletes often have resting heart rates of less than 60 beats per minute for example, champion bicycle racer Miguel Indurain reportedly had a resting heart rate of 28 beats per minute. This occurs because high-intensity training makes the heart muscle relatively powerful. Blood travels further through arteries and veins with each contraction, making fewer contractions necessary.
But slow heart rates may also indicate heart disease. Some individuals have a slow rate because of a problem within the heart’s electrical conduction system: the heart’s natural pacemaker is not working properly or the electrical pathways of the heart are disrupted.
In severe forms of bradycardia, the heart can beat so slowly that it doesn’t supply enough blood to meet the body’s needs. This can be life-threatening and often requires a pacemaker. A pacemaker is a medical device implanted in the chest that stimulates heart contractions via small electrical impulses.
A pacemaker can keep track of the heartbeat and generate electrical signals similar to that of the heart when it is operating normally, thus causing it to beat appropriately. Ultimately, the purpose of a pacemaker is to maintain heartbeats so that adequate oxygen and nutrients are delivered through the blood to the organs of the body.
What are the symptoms?
Some people with bradycardia have no symptoms, or their symptoms are so mild that they attribute them to the normal process of aging. An inappropriately slow heart rate results in insufficient blood flow to organs and tissues, which can ultimately lead to malfunction and organ failure. The one organ most affected by lack of oxygen and proper nutrients – particularly glucose – is the brain. Poor blood supply to the brain may cause a feeling of dizziness or lightheadedness, confusion and forgetfulness, poor memory and trouble concentrating or changes in consciousness. People can faint if a slow heart rate causes their blood pressure to drop critically.
Inadequate blood supply to muscles may lead to feeling short of breath, with decreased exercise tolerance, increased fatigue, cramping or diffuse muscle pain. Chest discomfort or heart palpitations – feeling one’s heart pounding or fluttering – can also be a sign of bradycardia.
You can determine how fast your heart is beating by taking your pulse. Feel your heartbeat at the base of your neck (just under the chin or on the underside of the wrist, below the base of the thumb). Count the number of beats in a minute. If your heartbeat is slow (less than 60 – about one beat per second, especially if you are not athletic) or uneven, talk to your doctor.
What are the causes?
The heart has its own electrical conduction system that regulates how fast and how hard it pumps. Electrical signals begin at the sinoatrial (SA) node – the heart’s natural pacemaker – located on the wall of the right atrium. Electrical signals from the SA node travel along the walls of the atria, causing atrial muscles to contract and pump blood into the lower chambers of the heart. These same electrical signals then travel to the AV node, a small area between the atria and ventricles that serves as an electrical relay station. From the AV node, these electrical signals travel along special conduction tissues to reach the walls of the ventricles, causing the ventricles to pump.
Bradycardia can result from diseases affecting the SA node, the conduction tissues, and the AV node. Sick sinus syndrome occurs when the SA node cannot generate signals frequently enough to maintain an adequate heart rate. Heart blocks of various degrees and heart failure can occur when cellular damage (due to high blood pressure and heart attacks) or age-related degeneration of the conduction system causes an impaired transmission of signals down through the heart muscle (myocardium). Certain medications can also cause bradycardia or worsen already existing disease. These include calcium channel blockers like nifedipine (Procardia) and verapamil (Calan) used for blood pressure regulation along with digoxin (Lanoxin), used for arrythmias and to treat heart failure and beta-blockers, such as atenolol (Tenormin) and propanolol (Inderal), used for hypertension and following myocardial infarction to protect surviving heart tissue.
The most common cause of bradycardia is degeneration of the conduction system due to aging. Thus, people are more likely to need a pacemaker as they get older, both as part of the aging process and because older patients tend to have additional medical problems that can cause slow heartbeats.
What is the conventional treatment?
If the patient has no symptoms, medical treatment may not be warranted. In some cases, the bradycardia is caused by medication, which if it can be safely stopped may cause the heart rate to normalize. However, because bradycardia is usually related to problems with cardiac conduction, the only method currently available to consistently increase heart rate is the use of a pacemaker.
Temporary pacemakers are usually used first, especially if the abnormally slow heart rate is thought to be a reversible condition that may be corrected. Temporary pacemakers are easily disconnected if the heart rate returns to normal.
Permanent pacemakers become necessary when bradycardia is believed to be a chronic or irreversible condition. Even though the overall heart rate may not be slow, pacemakers may also be used to treat fainting spells (syncope), congestive heart failure, hypertrophic cardiomyopathy, and other conditions where a controlled heartrate is desireable. It is implanted just under the skin of the chest wall in a relatively simple outpatient surgical procedure.
The pacemaker has two parts: the pulse generator and the leads. The pulse generator is implanted under the skin it houses the battery and a tiny computer that sets the pacing of the heart and keeps track of the pulse. The leads are wires connected to the pulse generator that are threaded through the veins into the heart and implanted into the heart muscle. They send impulses from the pulse generator to the heart muscle, as well as sensing the heart’s electrical activity. When the heart beats normally, the pacemaker does nothing however, if the heart stops beating or slows down, the pacemaker can take over at the selected rate. Typically, most implantable pacemakers have a battery that can last 10 to 15 years. The leads are relatively resistant to damage and pose little risk for infection or damage to heart tissue.
There are different types of pacemakers: single-chamber pacemakers use one lead in the upper chambers (atria) or lower chambers (ventricles) of the heart whereas a dual-chamber pacemaker uses one lead in the atria and one lead in the ventricles. A biventricular pacemaker uses three leads: one placed in the right atrium, one placed in the right ventricle, and one placed in the left ventricle. Your doctor will decide what type of pacemaker you need based on your heart condition.
Remember, most household electrical appliances do not interfere with pacemakers however, it is important to know which devices can cause interference with pacemaker signals. MRI machines and all magnetic devices that generate a strong magnetic field should be avoided. Cell phones can interfere with older style pacemakers and should be carried and used on the side of the body opposite to the side in which the pacemaker is implanted. Theft detector gates in stores can be a problem if individuals with pacemakers stand at or near them for long periods of time, but are probably not a problem if one walks quickly through them. Metal detectors at airports as well as handheld security wands can cause interference since they also generate magnetic fields. Individuals with pacemakers should present their ID card to security officers and walk around the gates. In pacemakers with older circuitry, high-powered electrical tools and running car engines can cause disturbances in electrical activity although most patients can drive a car, they should not lean over a running engine. Patients should check with their physicians if unsure about operating machinery or driving.
What therapies does Dr. Weil recommend for abnormal heart rhythm?
Nutritionally, Dr. Weil recommends an anti-inflammatory diet to anyone with cardiovascular disease, including daily Omega 3 fatty acid supplements, and eating two to three servings of fish – particularly oily species such as salmon or sardines – per week.
In addition, follow your doctor’s recommendations for heart health – quit smoking, watch your diet, and begin getting regular exercise. Control risk factors by working to address high blood pressure, diabetes and atherosclerosis, and reduce stress (the hormones released by the body in response to stress, anxiety and depression make the heart work harder). Practice relaxation techniques, volunteer, and seek positive social interactions. The Relaxing Breath can improve the oxygenation of blood and take workload off the heart.
Dr. Weil also recommends the following supplements if you are coping with heart-related issues:
- Coenzyme Q10(CoQ10). CoQ10 is a powerful antioxidant that has been shown to be beneficial for heart health by improving the utilization of oxygen at the cellular level. This nutrient is very important for the heart cells of patients with heart failure or tissue damage in the heart. CoQ10 may also help lower blood pressure.
- L-Carnitine. This amino acid is essential for energy metabolism of the heart muscle.
- Cordyceps. A medicinal mushroom that helps boost aerobic capacity and can improve the efficiency of the lungs and heart.
- Hawthorn. This herb, which should only be used under a doctor’s supervision, may increase heart-muscle strength and also act as a mild diuretic.
- D-Ribose. This naturally occurring five-carbon sugar has proven beneficial for maintaining adequate energy reserves in compromised heart tissue, and is especially recommended for those with congestive heart failure.
Be sure to discuss the use of any supplement with your doctor. Your prescription drug dosages may need to be adjusted as these other measures take effect.
Pacemakers can be categorized according to the NASPE coding system, that usually consists of 3-5 letters.
|Chamber(s) paced||Chamber(s) sensed||Response to sensing||Rate modulation||Multisite pacing|
|O = None||O = None||O = None||O = None||O = None|
|A = Atrium||A = Atrium||T = Triggered||R = Rate modulation||A = Atrium|
|V = Ventricle||V = Ventricle||I = Inhibited||V = Ventricle|
|D = Dual (A+V)||D = Dual (A+V)||D = Dual (T+I)||D = Dual (A+V)|
8 Pros and Cons of a Pacemaker
Pacemakers are often installed in people who are suffering from irregular heart rhythms. It is especially beneficial when that heart rhythm is irregular and slow. By adding an electrical impulse to the heart muscle when necessary, the heart rate is restored and blood circulates properly throughout the body. A successful installation can often completely eliminate the symptoms of bradycardia, relieving shortness of breath and chronic fatigue.
There are some advantages to having a pacemaker installed and there are some disadvantages that must be considered as well. Here is a look at the overall pros and cons of the procedure.
What Are the Pros of a Pacemaker?
1. Relief is almost immediate after the surgery has been completed.
People who have been suffering from bradycardia are often under a lot of physical stress because of their condition. They may not eat often, will have exercise intolerance, and may not even be able to drive. The pacemaker allows them to get their lives back on track right away because relief is experienced from the moment they wake up in the recovery room.
2. Pacemakers can be configured in a number of different ways.
Pacemakers can be programmed to control a wide variety of heartbeat issues that occur. They can help to beat the top heart chambers only, the bottom chambers, or both. Some pacemakers can even be programmed to stimulate both the left and right ventricles of the heart together.
3. They are a long-lasting device.
Most pacemakers are able to provide their needed therapy without maintenance for long periods of time. Only rarely are there wiring or battery failures that need to be addressed. Most of the risks that come with a pacemaker are due to the implantation surgery while the pacemaker is being placed. If that occurs successfully, almost all of the remainder of the risks are virtually eliminated.
4. Some models have electromagnetic resistance built into them.
Some of the newest models of pacemakers have countered the magnetic problems that have typically plagued this device. Although there are always going to be restrictions in place once the pacemaker has been installed, there are some devices that are safe in MRI machines and around certain appliances that could not be achieved in the past.
What Are the Cons of a Pacemaker?
1. People must avoid exposure to certain fields of energy.
Once a pacemaker is installed, magnetic and electromagnetic fields have to be avoided so that it will be able to continue to work properly. There will be a list of household appliances and tools which are allowed and disallowed that is provided to a patient after their surgery is successful. Even an unintentional failure to avoid appliances and devices that interfere with the pacemaker could have dire consequences.
2. Infection can happen after the surgery has been successful.
The surgery itself may be the cause of an infection that sets in around the pacemaker. An infection can also develop at the surgical site in the post-operation phase of recovery and then spread elsewhere in the body. A sensitivity to the materials that created the pacemaker may also lead to infection. Without treatment, these infections have the potential to be life-threatening.
3. The pacemaker may not work properly.
Pacemakers are very reliable after they’ve been installed and work consistently well for a majority of patients. There is a minority, however, that finds their pacemaker is not delivering the therapies that are required for proper health. When this occurs, a second surgery is necessary to replace the pacemaker so the proper therapy can be administered.
4. It does not treat heart disease.
The pacemaker is not a one-size-fits-all treatment solution for all heart problems. In particular it will not help to treat heart disease. Pacemakers may be installed after a heart attack to help control the rhythm of the heart muscle, but that won’t treat any underlying disease issues that may have contributed to the heart attack in the first place.
A Pacemaker Is Not a Cure.
It will not prevent a future heart attack or improve the foundations of cardiovascular health. It’s purpose is to treat an arrhythmia that is occurring with the heart’s beating cycle. In this it is effective, but it also means that there are certain conditions that cannot be treated by this device. This is why it is so important to go over all of the pros and cons of a pacemaker with a medical provider.
Indications of External Cardiac Pacing
Because of the ease and speed of implementation of transcutaneous pacing , it must not be forgotten in the emergency treatment of symptomatic bradycardia, provided its effectiveness is tested. 24-26 External transcutaneous pacing should not delay implementation of endocardial pacing, which can be applied for longer and more safely.
Single- and multiple-beat pacing stimulation has been described as a useful treatment of tachycardias. Overdrive pacing has been reported to terminate tachycardias using transcutaneous external pacemakers. Overall, termination rates for VT have been between 57% and 95% however, acceleration occurred in 4% to 26% of the reported attempts. Fisher et al reported termination in 57% and acceleration in 0.5% using single-beat capture compared with 94% termination and 3.6% acceleration in 3.6% using multiple-beat rapid-burst attempts. 27 This method is only justified in the context of an emergency. Termination of a tachycardia with endocardial pacing is safer and allows a better definition of the electrophysiologic profile of the tachycardia.
From a hemodynamic standpoint, studies have shown no difference in hemodynamics between transcutaneous pacemakers and transvenous pacemakers, using comparable rates in complete heart block and cardiac arrest. However, Madsen echocardiographically demonstrated in humans that atrial activation was retrograde. 28 Talit studied healthy volunteers with Doppler measurements and found that both stroke volume and cardiac output were reduced even when pacing at a rate 15% to 30% higher than the sinus baseline. 29 Thus, external pacing may need higher rates than expected in patients with symptomatic bradycardia to ensure that an adequate cardiac output is achieved.
No enzymatic, electrocardiographic, or histologic evidence of myocardial damage has been found after pacing (dogs and humans) for as long as 60 minutes. Few complications are associated with the use of transcutaneous external pacemakers. Pain is the most common side effect and, as noted previously, may be minimized by proper pad placement, use of the lowest effective current, and judicious administration of sedatives and analgesics. Coughing and hiccups may result from stimulation of the diaphragm and thoracic muscles. Skin burns have been reported with prolonged use. 30,31
Complications are not really to be feared. The most important condition for efficient external cardiac pacing is to ensure ventricular capture, something that is sometimes difficult to achieve. Potential causes include improper placement of the chest pads (directly over the sternum, scapula, or thoracic spine), poor skin contact (excessive hair, wet skin, or loosely applied pads), and inadequate current output. Anatomic impediments to current delivery may include fat (obesity), fluid (pericardial effusion), or air (pneumothorax, chronic obstructive pulmonary disease, or emphysema). 31 Electrocardiogram (ECG) monitoring is mandatory during noninvasive external pacing. As the current intensity applied to the patient's chest needs sometimes to be high to ensure ventricular capture, the pacing artifact seen on the monitor screen often suggests that stimulation is effective when it is not. The pacing artifact may mimic a QRS complex. However, a captured QRS is much wider than the noncapturing pacing artifact, and is followed by a T wave ( Fig. 20-22 ). If the doubt persists, the efficiency of external cardiac pacing can be confirmed by observation of a pulse wave following the pacing spike or of a ventricular contraction analyzed by echo. 32,33
Treat Atrial Fibrillation With Ablation and Pacemaker
If your heartbeat is out of whack from atrial fibrillation and medicine doesn't help, your doctor might suggest two high-tech solutions.
They may try to get your ticker's rhythm back in the right groove with a procedure called ablation. Or they may put a pacemaker in your chest -- a device that sends out pulses to keep your heartbeat on track. Some people need both methods.
Your doctor can help you decide which treatment is right for you, but learn as much as you can about the pros and cons. It will give you the confidence to move forward with a treatment plan that can get your heart pumping right.
Whatever you decide, it's important to get your AFib under control. When your heartbeat isn't regular -- or is too fast or too slow -- you're at a higher risk for blood clots and strokes.
It uses energy to destroy tiny areas of your heart muscle that set off the irregular rhythm. A doctor does the procedure in spots where AFib starts, which is often in your pulmonary veins. Those are the 4 blood vessel that carries oxygen-rich blood from the lungs to your heart.
It's rare, but sometimes you may need to have ablation of the AV node. It's the place that electrical signals pass through as they travel from the upper to the lower heart chambers.
Doctors may do ablation there if you have very rapid atrial fibrillation that you can't control with medication. But if you get the procedure in your AV node, your heartbeat may become too slow. You'll need to get a pacemaker put into your chest.
What Happens During Ablation?
Your doctor puts long, thin tubes called catheters into blood vessels in your leg or neck, and then guides them to your heart. One catheter has an ultrasound at the end -- a device that uses soundwaves to let the doctor see an image of your ticker.
During the procedure, energy from radio waves or lasers travels through the catheter. It burns the parts of your heart that cause the messed-up electrical signals that trigger your rhythm problems. After a few weeks, scars form in those spots, which stop the faulty signals and bring back a steady heart rhythm.
Pros. There are lots of good reasons to have an ablation. It can often stop AFib, and it can also:
- Help prevent blood clots and strokes
- Relieve shortness of breath and tiredness
- Reduce your need for blood thinners and heart rhythm drugs
- Help you exercise more often and for longer amounts of time
- Improve the length and quality of your life
For some folks, ablation restores a normal heart rhythm better than medicine.
Cons. Ablation is generally safe, but it does have some risks. Some of the things that can go wrong are:
- Bleeding around your heart or where the catheter is inserted
- Hole in the heart
- Narrowing of the pulmonary vein
- Damage to the esophagus, the tube that carries food from your mouth to your stomach
Also, your AFib can come back in the first few months after you have ablation. In that case, you may need to have the procedure again, or take heart rhythm drugs.
It's a small device that monitors your heartbeat and sends out a signal to stimulate your heart if it's beating too slowly. Pacemakers are used to treat a slow heartbeat in people with AFib.
The device is made up of a small box called a generator. It holds a battery and tiny computer.
Very thin wires called leads connect the pacemaker to your heart. Impulses flow through the leads to keep the organ in rhythm.
What Happens When You Get a Pacemaker?
It may sound like a big deal, but it's a minor procedure. First, your doctor inserts a needle into a large vein near your shoulder, which guides the leads into your heart.
The pacemaker then goes into your chest through a small cut. Once it's in place, your doctor tests it to make sure it works.
Pros. Your doctor can program your pacemaker to meet your needs. It should keep your heart in rhythm and help you stay more active.
Cons. The surgery to put in the device is safe, but there are some risks, such as:
- Bleeding or bruising in the area where your doctor places the pacemaker
- Damaged blood vessel
- If there are problems with the device, you may need another surgery to fix it.
Sometimes the impulses your pacemaker sends to your heart can cause discomfort. You may be dizzy, or feel a throbbing in your neck.
Once you have one put in, you might have to keep your distance from objects that give off a strong magnetic field, because they could affect the electrical signals from your pacemaker.
Some devices that can interfere with it are:
- Metal detectors
- Cell phones and MP3 players
- Electric generators
- Some medical machines, such as an MRI
Your doctor will help you choose the right treatment based on your health. Talk over the risks and benefits with them, and weigh them carefully before you make up your mind.
AHRQ: "Radiofrequency Ablation for Atrial Fibrillation: A Guide for Adults."
American Heart Association: "Non-surgical procedures for atrial fibrillation," "What is Atrial Fibrillation (AFib or AF)?"
Cleveland Clinic: "Pulmonary vein isolation ablation."
Haegeli, Laurent M. European Heart Journal, July 2014.
January, Craig T. Circulation, 2014.
Massachusetts General Hospital: "Catheter Ablation for the Treatment of Atrial Fibrillation."
Mount Sinai St. Luke's: "A patient guide to atrial fibrillation and catheter ablation."
National Heart, Lung, and Blood Institute: "How Does a Pacemaker Work?" "How Will a Pacemaker Affect My Lifestyle?" "What are the Risks of Pacemaker Surgery?" "What to Expect During Pacemaker Surgery."
The Society of Thoracic Surgeons: "HRS/EHRA/ECAS Expert Consensus Statement on Catheter and Surgical Ablation of Atrial Fibrillation: Recommendations for Personnel, Policy, Procedures, and Follow-Up."
The University of Chicago Medicine: "Surgical Treatment for Atrial Fibrillation."
A complete pacemaker check should be done six weeks after your pacemaker is implanted. This follow-up appointment is critical, because adjustments will be made that will prolong the life of your pacemaker. Then your pacemaker should be checked every three months on the telephone to evaluate battery function. Your nurse will explain how to check your pacemaker using the telephone transmitter. Once or twice a year you will need a more complete exam.
If you have a biventricular pacemaker, you may need to visit the doctor's office or hospital more frequently to make sure your device is working properly and the settings do not need to be adjusted.