Can you feel a pulse with an LVAD? Doppler Blood Pressure Explained

Have you ever reached for the LVAD patient’s wrist to check their pulse and felt nothing? That is when panic sets in, and you start questioning if the device is working properly or has failed to do its job. Or you start to think about taking essential steps by thinking that they might be in danger. If your loved one is with an LVAD, this moment can be terrifying. But here is the truth: the absence of a pulse in an LVAD patient does not mean the absence of life.

For most of the LVAD patients, the device is still working and supplying enough blood without generating a pulse like a normal human heart does. Let’s understand how and why it happens. And what are the ways to measure blood pressure in such patients? This will help you have enough information so you can manage daily care without suspecting false emergency situations.

What is an LVAD, and how does it affect your Blood Flow?

A Left Ventricular Assist Device (LVAD) is a medical device that is implanted inside the heart and assists the Heart to pump blood and supply all over the body. LVAD consists of internal components like the LVAD pump, which is surgically implanted in the left ventricle of the heart, and a driveline that exits the abdominal area to connect to the controller outside. The external components, like batteries and the controller, stay outside the body, and patients need to carry them all the time. 

Unlike a natural heartbeat, the modern LVAD device works through continuous flow technology. It means the device moves blood in a constant stream rather than in the push-and-pause pattern. As a result, blood circulates and provides oxygen to the brain and other organs in the body. You may not feel the natural ‘lub-dub’ pulse like you do at the wrist, neck, or chest of a healthy person.

Why can’t you feel a pulse in most LVAD patients like a normal person?

To understand why the pulse disappears, you must know about what creates a pulse in the first place. When a healthy heart beats, the heart muscles contract and push blood into the arteries. This creates a pressure wave inside the blood vessels. Between two heartbeats, pressure drops, and this rhythmic rise and fall is what creates a pulse.

Now, if we talk about an LVAD patient, the continuous flow of blood cannot create a rhythm. So, instead of pushing blood in bursts, the device pumps blood at a constant speed. Normally, it can spin around thousands of revolutions per minute and creates a smooth blood flow. As there is no drop or rise in blood pressure, there will be no detectable pulse at the wrist or neck.

In some of the LVAD patients, whose hearts are functioning partially, a faint pulse may be present. The Heart is weak but still able to contract, so it creates a slight pressure variation with the steady flow of the device. But in patients with severely reduced cardiac function, the heart barely contributes to pumping blood and the pulse disappears entirely.

How do you measure Blood pressure in an LVAD patient?

Standard ways of measuring blood pressure, as you experience in healthcare settings, cannot be used in an LVAD patient. Measuring blood pressure through cuffs depends on pulsatile blood flow, which is absent in LVAD patients. So, without a pulse, these machines can provide false readings and produce a result that indicates an emergency. This is not a minor inconvenience. Relying on incorrect blood pressure data in an LVAD patient can either mask an emergency situation or create a panic of suspecting a false alarm. Both of which carry serious consequences.

Mean Arterial Pressure (MAP)

Mean arterial pressure (MAP) is the average pressure in the arteries throughout the entire cardiac cycle. Instead of using the traditional method to measure e blood pressure, clinicians use Mean Arterial Blood pressure as an accurate method for LVAD patients. This provides more accurate results when there is no pressure difference to measure. 

For LVAD patients, the mean arterial pressure (MAP) target range is 70 to 90 mmHg. However, individual targets can be set by the LVAD care team based on the specific type of patient and general health.

What is LVAD Doppler Blood Pressure?

Doppler pressure measurements use high-frequency sound waves to detect the movement of red blood cells inside an artery. 

Doppler blood pressure measurement uses high-frequency sound waves to detect the movement of red blood cells within an artery. Even when blood flows continuously without pulsatile variation, the Doppler probe picks up that movement and identifies the precise moment arterial flow begins as cuff pressure is released — giving a reliable MAP reading.

This technique works because it does not depend on pressure oscillations. It simply listens for flow, making it the gold standard for blood pressure monitoring in continuous-flow LVAD patients.

Step-by-Step Procedure

Here is a procedure for checking the blood pressure of an LVAD patient with a Doppler:

• Prepare:

• Here are some of the things you will need: a blood pressure cuff, a handheld Doppler probe, and ultrasound gel. Make sure the patient is in a comfortable seated or lying position and has not engaged in any physical activity for the past 5 minutes. Also, remove any tight clothing from the upper arm.

• Place the Cuff:

• Apply the blood pressure cuff to the upper arm in the standard position, which is approximately one inch above the inner crease of the elbow. The cuff should fit snugly and should not be too tight or restrictive.

• Locate the Pulse:

• Apply ultrasound gel to the inside of the elbow over the crease. Place the probe or wand of the Doppler machine against the skin and move it slowly until you find the sound of the whooshing of blood inside the artery.

• Inflating the cuff:

• Once you begin to hear the blood flow, start inflating the cuff and stop approximately 20 mmHg above the point where the Doppler sound disappears. It can vary from patient to patient.

• Deflate and Read:

• Now slowly release the cuff pressure at a rate of 2 to 3 mmHg per second. Record the reading from the cuff gauge exactly the moment you hear the blood flow again. This is Mean Arterial Pressure (MAP). Record this value. 

What does MAP Reading mean?

• MAP Value below 50 mmHg: Blood pressure is critically low and indicates hypoperfusion.

• 50 to 69 mmHg: Blood pressure is low and needs proper care

• 70 to 90 mmHg: This is the normal range for most of the LVAD patients

• Above 90 mmHg: Blood pressure is dangerously high, and there is a risk of stroke or LVAD device malfunction.

Factors That Influence Pulse Detectability

Every LVAD patient is unique and doesn’t have the same medical conditions as all other LVAD patients. Various medical, individual, and general health factors can vary. Several factors are here that affect whether a faint pulse can be detected:

Residual heart function: Patients whose heart is still functioning slightly may hear the pulse. They may have a weak but detectable pulse.

Device Setting: The doctors adjust the LVAD pump speed according to the native heart function. Higher speed in the LVAD pump increases the circulation and can reduce the pulse detection.

Dehydration: Low volume of blood and conditions like dehydration can significantly reduce blood pressure and pulse detection.

Other heart conditions:  LVAD patients who have other medical conditions, like peripheral vascular disease, may require probe repositioning and a professional’s expertise to detect blood pressure.

It is important to understand these variables, which help caregivers to avoid taking action in the absence of a pulse, which is completely normal. However, you should stay alert to genuinely abnormal changes in the patient.

Common Myths about LVAD Pulse and Blood Pressure

Many people don’t know that the pulse being absent in an LVAD patient may not always be an emergency situation, and because of that, there are various myths regarding the situation. Some of the myths about LVAD patients’ pulse and blood pressure are:

• Myth: The absence of a pulse means the heart or device has stopped functioning completely.

A pulseless LVAD patient may be perfectly stable, and the device may perform accurately.

• Myth: A regular blood pressure cuff can be used to check the BP of an LVAD patient.

LVAD patients’ BP cannot be checked with traditional methods, as it may require a proper Doppler device.

• Myth: If the LVAD device is working properly, the body gets its normal blood supply.

Although it may be true for most cases, sometimes the patient is dehydrated or has another condition that affects the perfusion rate. 

• Myth: You only need to check blood pressure if something feels off.

It is essential to check blood pressure (MAP) regularly, even if the patient feels well. Persistent increased blood pressure can increase the risk of stroke. 

Everyday Life with an LVAD

Living with an LVAD is entirely manageable; all you need to do is learn safe techniques and put the right habits in place. The goal is not to live in constant fear of handling the device, but to build a modified lifestyle and safe routine that has both peace of mind and safe accommodation. 

The foundation of long-term safety is detecting signs of complications such as infection and bleeding. Check for the batteries that are fully charged. Also, keep an extra pair of batteries. Follow the clinic visits that are scheduled by your care team. Keep a record of your blood pressure readings, as they tell a lot about your health. Understand device alarms so that you can manage your device accordingly.

One essential accessory for managing the LVAD device safely is the right LVAD gear. Wearing an LVAD vest or LVAD shirt not only secures your device in place but also lets you move freely with peace of mind.

Final Thoughts

If you are caring for someone with an LVAD, it is important to understand that not feeling a pulse does not mean something is wrong. The LVAD works differently from a normal heart, providing continuous blood flow without the usual heartbeat. Since traditional methods for measuring blood pressure rely on the pulse, it is essential to use techniques like Mean Arterial Pressure (MAP) or Doppler measurements for accurate readings. This knowledge will help you confidently manage their care and avoid unnecessary panic. Always work closely with the healthcare team to ensure proper monitoring and support for the patient.

Frequently Asked Questions (FAQs)

Is it normal to feel no pulse in an LVAD patient?

Yes. Most of the LVAD patients have little to no detectable pulse. This can be expected in an LVAD patient and does not indicate a problem on its own.

How often should I check MAP at home?

Most LVAD programs recommend at least once daily, or as directed by the care team. Always check the MAP if the patient reports dizziness, fatigue, or if the controller sounds an alarm. 

Can I use a home blood pressure monitor for an LVAD patient?

Standard automatic monitors are unreliable for LVAD patients. A manual cuff with a handheld Doppler device is the recommended home monitoring method. Confirm this with your LVAD coordinator. 

What is the most important thing a caregiver can do for an LVAD patient?

Stay educated, stay consistent, and stay connected to the care team. Daily monitoring, prompt alarm response, and regular clinic attendance prevent the majority of serious LVAD complications.