Human Blood Flow
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Human Heart
Anterior View
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Heart Procedures Offered by the Staff of Northwest Houston Heart Center

1) What is an electrocardiogram?

An electrocardiogram (ECG or EKG) is one of the simplest and fastest procedures used to evaluate the heart. Electrodes (small, plastic patches) are placed at certain locations on the chest, arms, and legs. When the electrodes are connected to an ECG machine by very low voltage electrical wires, the electrical activity of the heart is measured, interpreted, and printed out for the physician's information and further interpretation. This provide your physician valuable information regarding the condition of your heart.

2) What is an exercise electrocardiogram?

An exercise ECG is performed to assess the heart's response to stress or exercise. The ECG is monitored while a person is exercising on a treadmill or stationary bike.

An ECG tracing will be taken at certain points during the test in order to compare the effects of increasing stress on the heart. Periodically, the incline and treadmill speed will be increased in order to make exercise more difficult for the person being tested. If the person is riding a bicycle, he/she will pedal faster against increased resistance. In either circumstance, the person will exercise until reaching a target heart rate (determined by the physician based on age and physical status) or until unable to continue due to fatigue, shortness of breath, chest pain, or other symptoms. Other related procedures that may be used to assess the heart include resting electrocardiogram (ECG), Holter monitor, signal-averaged ECG, cardiac catheterization, chest x-ray, computed tomography (CT scan) of the chest, echocardiography, electrophysiological studies, magnetic resonance imaging (MRI) of the heart, myocardial perfusion scans, radionuclide angiography, and ultra fast CT scan. Please see these procedures for additional information.

3) What is a Holter monitor?

The Holter monitor is a type of electrocardiogram (ECG or EKG) used to monitor the ECG tracing continuously for a period of 24 hours or longer. When symptoms such as dizziness, fainting, low blood pressure, prolonged fatigue, and palpitations continue to occur without a definitive diagnosis obtained with a resting ECG, an exercise ECG, your physician may request an ECG tracing to be run over a long period of time, using the Holter monitor. Certain dysrhythmias/arrhythmias (abnormal heart rhythms), which can cause the symptoms noted above, may occur only intermittently, or may occur only under certain conditions, such as stress. Dysrhythmias of this type are difficult to obtain on an ECG tracing that only runs for a few minutes. Thus, the physician will request a Holter monitor to allow a better opportunity to capture any abnormal beats or rhythms that may be causing the symptoms. The Holter monitor records continuously for the entire period of 24 to 48 hours. Some Holter monitors may record continuously but also have an event monitor feature that you activate when symptoms begin to occur.

You will receive instructions regarding how long you will need to wear the recorder (usually 24 to 48 hours), how to keep a diary of your activities and symptoms during the test, and personal care/activity instructions.

4) What is an event monitor?

Event monitoring is very similar to Holter monitoring, and is often ordered for the same reasons. With an event monitor, you wear ECG electrode patches on your chest, and the electrodes are connected by wire leads to a recording device. Unlike the Holter monitor, however, which records continuously throughout the testing period of 24 to 48 hours, the event monitor does not record until you feel symptoms and trigger the monitor to record your ECG tracing at that time.

When you feel one or more symptoms, such as chest pain, dizziness, or palpitations, you push a button on the event monitor recorder. Some monitors have a feature (memory loop recorder) which captures a short period of time prior to the moment you triggered the recording and afterwards. This feature can help your physician determine more details about the possible change in your ECG at the time the symptoms started, and what was happening with your ECG just before you triggered the recorder. Other monitors, called "post-event recorders," simply start recording your ECG from the moment you trigger it.

Post-event recorders are quite small about the size of a pager or cell phone.

After you experience symptoms and record them, you will send the recording of the event to your physician or to a central monitoring center. This transmission is done over the telephone. You will be instructed regarding how to do this on the recorder. You will also keep a diary of your symptoms and corresponding activities (as done during the Holter monitoring procedure)

5) What is an echocardiogram?

An echocardiogram is a noninvasive and painless (the skin is not pierced) procedure used to assess the heart's function and structures. During the procedure, a transducer (like a microphone) sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer is placed on the chest at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the heart tissues, where the waves echo off of the heart structures. The transducer picks up the reflected waves and sends them to a computer. The computer interprets the echoes into an image of the heart walls and valves.

6) What is a stress myocardial perfusion scan (Nuclear Stress Test) ?

A myocardial perfusion scan is a type of nuclear medicine procedure. This means that a tiny amount of a medically safe radioactive substance, called a radionuclide (radiopharmaceutical or radioactive tracer), is used during the procedure to assist in the examination of the tissue under study. Specifically, the myocardial perfusion scan evaluates the heart’s function and blood flow.

A radionuclide is a radioactive substance used as a "tracer," which means it travels through the blood stream and is taken up (absorbed) by the healthy heart muscle tissue. On the scan, the areas where the radionuclide has been absorbed will show up differently than the areas that do not absorb it (due to decreased blood flow to the area or possible damage to the tissue from decreased or blocked blood flow).

A stress myocardial perfusion scan is used to assess the blood flow to the heart muscle (myocardium) when it is stressed by exercise or medication and to determine what areas of the myocardium have decreased blood flow. This is done by injecting a radionuclide (thallium or technetium) into a vein in the arm or hand.

There are different types of radionuclides. When one type of radionuclide is used, areas of the myocardium that have blocked or partially blocked arteries will be seen on the scan as "cold spots," or "defects," because these areas will be unable to take in the radionuclide into the myocardium. Another type of radionuclide binds to the calcium that is released when a heart attack occurs, so it will accumulate in area(s) of injured heart tissue as a “hot spot” on the scan.

There are two types of stress myocardial perfusion scans, one that is used in conjunction with exercise (myocardial perfusion scan with exercise) and one that is used in conjunction with medication (pharmacologic myocardial perfusion scan).

• Myocardial perfusion scans with exercise
• A myocardial perfusion scan with exercise is used to determine what areas of the heart muscle (myocardium) have decreased blood flow during exercise. This is done by injecting a radionuclide (thallium or technetium) into a vein in the arm or hand during exercise. After the radionuclide has been injected into a vein and has circulated through the blood stream, a special machine called a gamma camera takes pictures of the heart while the person lies still on a table. This scanning usually lasts about 15 minutes.
• Any areas of the myocardium that have blocked or partially blocked arteries during exercise will be seen on the scan as "cold spots," or "defects," because these areas will be unable to absorb the radionuclide into the myocardium.
• A second set of scans is taken at rest. The resting phase is done in order to compare the results with the exercise phase to see if areas that do not get adequate blood flow while exercising are able to absorb the radionuclide during rest.
• Myocardial perfusion scans with pharmacologic intervention
• A pharmacologic myocardial perfusion scan is used when the physician has determined that exercise on a treadmill is not an appropriate choice due to the person’s medical condition. In this situation, a medication is given that causes the coronary arteries to dilate. This dilation of the coronary arteries increases blood flow and are very similar to the response of the arteries during exercise. The medication is injected into a vein in the arm or hand.
• After a given period of time, the radionuclide will be injected into a vein in the arm or hand. The gamma camera will take pictures of the heart while the person lies still on a table. A resting scan will be performed afterwards, just as with the actual exercise scan.

Coronary Artery Disease:

Coronary artery disease (CAD) is the narrowing of the coronary arteries (the blood vessels that supply oxygen and nutrients to the heart muscle), caused by a buildup of fatty material within the walls of the arteries. This buildup causes the inside of the arteries to become rough and narrowed, limiting the supply of oxygen-rich blood to the heart muscle.

To better understand how coronary artery disease affects the heart, a review of basic heart anatomy and function follows.

The heart is basically a pump. The heart is made up of specialized muscle tissue, called the myocardium. The heart's primary function is to pump blood throughout the body, so that the body's tissues can receive oxygen and nutrients and have waste substances taken away.

Fortunately, the technology is available to restore blood flow to heart tissue when coronary artery blockages are diagnosed. One of several diagnostic procedures used to diagnose and evaluate coronary artery disease is the myocardial perfusion scan.

Reasons for the Procedure

Indications for an exercise or pharmacologic myocardial perfusion scan may include, but are not limited to, the following: chest pain, or shortness of breath either new onset or occurring over a period of days or longer.

To diagnose coronary artery disease

To assess viability of heart muscle

Evaluation of cardiac risk before non cardiac surgery following a heart attack (myocardial infarction, or MI) to assess blood flow to areas of the myocardium that have been reperfused (coronary artery blood flow restored) by bypass surgery, angioplasty (the opening of a coronary artery using a balloon or other method), or stent (a tiny expandable metal coil placed inside an artery to keep the artery open)

There may be other reasons for your physician to recommend a myocardial perfusion scan.

During the Procedure

A stress myocardial perfusion scan may be performed on an outpatient basis or as part of your stay in a hospital. Procedures may vary depending on your condition and your physician's practices.

Generally, a stress myocardial perfusion scan follows this process:

• You will be asked to remove any jewelry or other objects that may interfere with the procedure.
• If you are asked to remove clothing, you will be given a gown to wear.
• An intravenous (IV) line will be started in your hand or arm.
• You will be connected to an ECG machine with leads and a blood pressure cuff will be placed on your arm.>

Exercise myocardial perfusion scan:

• You will exercise on a treadmill. The intensity of the exercise will be gradually increased by increasing the speed of the treadmill.
• Your heart rate and blood pressure will be monitored. Once you have reached your maximal exercise point (determined by the physician based on your heart rate and age), the radionuclide will be injected into your IV line.
• After the radionuclide has been injected, you will continue to exercise for one to two minutes.

Pharmacologic Myocardial Perfusion Scan:

• You will not exercise on a treadmill. Instead, you will lie on the table while a medication is injected into your IV to increase your heart rate.
• Your heart rate and blood pressure will be monitored.
• Once you have reached your target heart rate, the radionuclide will be injected into your IV line.

Procedure completion, both methods:

• If you experience any symptoms such as dizziness, chest pain, shortness of breath, or severe fatigue at any point during the procedure, let the physician or technologist know.
• You will lie flat on a table while the images of your heart are obtained. Approximately 10 to 60 minutes after the radionuclide is injected, the gamma camera will begin to take pictures of your heart. In a special kind of test called SPECT (single photon emission computed tomography), the scanner will rotate around you as it takes pictures.
• Your arms will be positioned above your head. It will be necessary for you to lie very still while the images are being taken, as movement can adversely affect the quality of the images.
• After the scan is completed, you may be allowed to leave the area, but will need to return at the appropriate time for a second set of scans. During this time, you will not be allowed to eat, unless specifically instructed to do so by the technologist, and will be allowed limited water or decaffeinated/non-caloric liquids. Your physician may decide to have you return on another day for the second set of scans.
• The second set of scans will be similar to the first set - you will lie on the table as before while the scanner takes pictures of your heart.
• Once the second set of scans has been completed, the IV line will be discontinued, and you will be allowed to leave, unless your physician instructs you differently.

After the Procedure

You should move slowly when getting up from the scanner table to avoid any dizziness or lightheadedness from lying flat for the length of the procedure.

You will be instructed to drink plenty of fluids and empty your bladder frequently for 24 to 48 hours after the test to help flush the remaining radionuclide from your body.

The IV site will be checked for any signs of redness or swelling. If you notice any pain, redness, and/or swelling at the IV site after you return home following your procedure, you should notify your physician as this may indicate an infection or other type of reaction.

Your physician may give you additional or alternate instructions after the procedure, depending on your particular situation.

What is a Resting Myocardial Perfusion Scan?

A myocardial perfusion scan is a type of nuclear medicine procedure. This means that a tiny amount of a radioactive substance, called a radionuclide (radiopharmaceutical or radioactive tracer), is used during the procedure to assist in the examination of the tissue under study. Specifically, the myocardial perfusion scan evaluates the heart’s function and blood flow.

A radionuclide is a radioactive substance used as a "tracer," which means it travels through the blood stream and is taken up (absorbed) by the healthy heart muscle tissue. On the scan, the areas where the radionuclide has been absorbed will show up differently than the areas that do not absorb it (due to decreased blood flow to the area or possible damage to the tissue from decreased or blocked blood flow).

A resting myocardial perfusion scan is used to assess the blood flow to the heart muscle (myocardium) and to determine what areas of the myocardium have decreased blood flow. This is done by injecting a radionuclide (thallium or technetium) into a vein in the arm or hand.

There are different types of radionuclides. When one type of radionuclide is used, areas of the myocardium that have blocked or partially blocked arteries will be seen on the scan as "cold spots," or "defects," because these areas will be unable to take in the radionuclide into the myocardium. Another type of radionuclide binds to the calcium that is released when a heart attack occurs, so it will accumulate in area(s) of injured heart tissue as a “hot spot” on the scan.

7) What are Vascular Studies?

Vascular studies are a noninvasive and painless (the skin is not pierced) procedure used to assess the blood flow in arteries and veins. A transducer (like a microphone) sends out ultrasonic sound waves at a frequency too high to be heard. When the transducer is placed on the skin at certain locations and angles, the ultrasonic sound waves move through the skin and other body tissues to the blood vessels, where the waves echo off of the blood cells. The transducer picks up the reflected waves and sends them to an amplifier, which makes the ultrasonic sound waves audible.

Vascular studies can utilize one of these special types of ultrasound technology, as listed below:

To assess the carotid arteries in the neck, a carotid duplex scan may be performed. This type of Doppler examination provides a 2-dimensional (2D) image of the arteries so that the structure of the arteries and location of an occlusion can be determined, as well as the degree of blood flow.

A carotid artery duplex scan is a type of vascular ultrasound study done to assess occlusion (blockage) or stenosis (narrowing) of the carotid arteries of the neck and/or the branches of the carotid artery. Plaque (a buildup of fatty materials), a thrombus (blood clot), and other substances in the blood stream may cause a disturbance in the blood flow through the carotid arteries.
 

More severe symptoms, such as sudden sharp headache, loss of vision in one eye, sudden loss of ability to move arms, legs, or one side of the body, sudden forceful vomiting, or sudden decreased level of consciousness may mean that a stroke is imminent.

Some conditions which may affect blood flow include, but are not limited to, the following:

• Atherosclerosis - a gradual clogging of the arteries over many years by fatty materials and other substances in the blood stream
• aneurysm - a dilation of a part of the heart muscle or the aorta (the large artery that carries oxygenated blood out of the heart to the rest of the body), which may cause weakness of the tissue at the site of the aneurysm
• embolus or thrombus - clots in blood vessels may be either an embolus (a small mass of material such as fat globules, air, clusters of bacteria, or even foreign matter such as a piece of metal from a bullet) or a thrombus (a blood clot)
• inflammatory conditions - an inflammation within a blood vessel may occur as a result of trauma (physical trauma, such as from a fall, or chemical trauma, such as from an irritating medication being introduced into the vessel), infection, or an autoimmune disorder (e.g., polyarteritis, Raynaud's disease, and aortic arch syndrome)
• varicose veins - occur when the veins of the circulatory system in the legs are exposed over time to pressure that causes stress on the walls and valves of the veins

Any of these conditions may cause decreased blood flow in arteries and/or veins. Some symptoms that may occur when blood flow decreases to the legs include, but are not limited to, the following:

• leg pain and/or weakness during exertion (known as claudication)
• swelling
• soreness, tenderness, redness, and/or warmth in the leg(s)
• pale and cool skin; may even be grayish or blue
• numbness or tingling
• rest pain (pain in the foot that occurs when sitting or lying down and is relieved by standing)
• If the physician suspects that a person may have decreased blood flow somewhere in the peripheral (arms, legs, and/or neck) circulation, vascular studies may be performed.

 Reasons for the Procedure

Reasons for which vascular studies may be performed include, but are not limited to, the following:

• Evaluation of signs and symptoms which may suggest decreased blood flow in the arteries and/or veins of the neck, legs, or arms
• Evaluation of previous procedures that were performed to restore blood flow to an area
• Evaluation of a vascular dialysis device, such as an A-V fistula in the arm
• There may be other reasons for your physician to recommend a vascular study.

 Before the Procedure

• Your physician will explain the procedure to you and offer you the opportunity to ask any questions that you might have about the procedure.
• Generally, no prior preparation, such as fasting or sedation, is required.
• Your physician may give you specific instructions about smoking and consuming caffeine. You may be asked to refrain from smoking for at least two hours before the test, as smoking causes blood vessels to constrict. You may also be asked to refrain from consuming caffeine in any form for about two hours prior to the test.
• Based upon your medical condition, your physician may request other specific preparation
   

8) What is a Pacemaker/Implantable Cardioverter Defibrillator                  (ICD) Insertion?

 A pacemaker/implantable cardioverter defibrillator (ICD) insertion is a procedure in which a pacemaker and/or an ICD is inserted to assist in regulating problems with the heart rate (pacemaker) or heart rhythm (ICD).

 Pacemaker:

When a problem develops with the heart’s rhythm, such as a slow rhythm, a pacemaker may be selected for treatment. A pacemaker is a small electronic device composed of three parts: a generator, one or more leads, and an electrode on each lead. A pacemaker signals the heart to beat when the heartbeat is too slow.

Pacemaker leads may be positioned in the atrium or ventricle or both, depending on the condition requiring the pacemaker to be inserted. An atrial dysrhythmia/arrhythmia (an abnormal heart rhythm caused by a dysfunction of the sinus node or the development of another atrial pacemaker within the heart tissue that takes over the function of the sinus node) may be treated with an atrial pacemaker.

Implantable cardioverter defibrillator (ICD):

An implantable cardioverter defibrillator (ICD) looks very similar to a pacemaker, except that it is slightly larger. It has a generator, one or more leads, and an electrode for each lead. These components work very much like a pacemaker. However, the ICD is designed to deliver an electrical shock to the heart when the heart rate becomes dangerously fast, or “fibrillates.”

An ICD senses when the heart is beating too fast and delivers an electrical shock to convert the fast rhythm to a normal rhythm. Some devices combine a pacemaker and ICD in one unit for persons who need both functions.

The ICD has another type of treatment for certain fast rhythms called anti-tachycardia pacing (ATP). When ATP is used, a fast pacing impulse is sent to correct the rhythm. After the shock is delivered, a “back-up” pacing mode is used if needed for a short while.

The procedure for inserting a pacemaker or an ICD is the same. The procedure generally is performed in an electrophysiology (EP) lab or a cardiac catheterization lab.

Implantable cardioverter defibrillator (ICD):

An implantable cardioverter defibrillator (ICD) looks very similar to a pacemaker, except that it is slightly larger. It has a generator, one or more leads, and an electrode for each lead. These components work very much like a pacemaker. However, the ICD is designed to deliver an electrical shock to the heart when the heart rate becomes dangerously fast, or “fibrillates.”

An ICD senses when the heart is beating too fast and delivers an electrical shock to convert the fast rhythm to a normal rhythm. Some devices combine a pacemaker and ICD in one unit for persons who need both functions.

The ICD has another type of treatment for certain fast rhythms called anti-tachycardia pacing (ATP). When ATP is used, a fast pacing impulse is sent to correct the rhythm. After the shock is delivered, a “back-up” pacing mode is used if needed for a short while.

The procedure for inserting a pacemaker or an ICD is the same. The procedure generally is performed in an electrophysiology (EP) lab or a cardiac catheterization lab.

9) What is percutaneous transluminal coronary angioplasty and Coronary Stent ?

A small sample of heart tissue (called a biopsy) may be obtained during the procedure to be examined later under the microscope for abnormalities.

A technique called intravascular ultrasound (IVUS), a technique that uses a computer and a transducer that sends out ultrasonic sound waves to create images of the blood vessels, may be used during PTCA. The use of IVUS provides direct visualization and measurement of the inside of the blood vessels and may assist the physician in selecting the appropriate size of balloons and/or stents, to ensure that a stent, if used, is properly opened, or to evaluate the use of other angioplasty instruments.

The physician may determine that another type of procedure is necessary. This may include the use of atherectomy (removal of plaque) at the site of the narrowing of the artery. In atherectomy, there may be tiny blades on a balloon or a rotating tip at the end of the catheter. When the catheter reaches the narrowed spot in the artery, the plaque is broken up or cut away to open the artery. Atherectomy is used when the plaque is calcified, hardened, or if the vessel is completely closed. Another type of atherectomy procedure uses a laser, which opens the artery by "vaporizing" the plaque.

What is stent placement?

In the past few years, many refinements have been developed in the PTCA procedure. One common procedure used in PTCA is stent placement. A stent is a tiny, expandable metal coil that is inserted into the newly-opened area of the artery to help keep the artery from narrowing or closing again.

newly stented blood vessel. If scar tissue does form inside the stent, radiation therapy (called brachytherapy) may be used to clear the scarred area and open up the vessel.

ICG (Impedance Cardiography)

Every day, clinicians prescribe cardiovascular medications that affect blood flow forces, or hemodynamics. Until recently, obtaining hemodynamic information required invasive monitoring in a hospital setting, leaving clinicians in the office with poor surrogates such as blood pressure and heart rate.

Noninvasive BioZ® utilizes Impedance Cardiography (ICG) to quickly provide hemodynamic information and is clinically proven to assist in diagnosis, prognosis, and therapy for patients with:

How ICG Works:

• Disposable sensors transmit a small electrical signal through the thorax
• Impedance (resistance) to the electrical signal is measured and displayed as the ICG waveform
• As volume and velocity of blood in the aorta change with each heartbeat, DISQ® (Digital Impedance Signal Quantifier) Technology processes the changes in impedance
• The changes in impedance are applied to the innovative Z MARC® (Modulating Aortic Compliance) Algorithm to provide hemodynamic parameters including:
   
• Cardiac Output
• Stroke Volume
• Systemic Vascular Resistance
• Contractility
• Fluid Status