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What Is Blood Pressure? Blood pressure is the force of blood against the walls of arteries. Blood pressure is recorded as two numbers—the systolic pressure (as the heart beats) over the diastolic pressure (as the heart relaxes between beats). The measurement is written one above or before the other, with the systolic number on top and the diastolic number on the bottom. For example, a blood pressure measurement of 120/80 mmHg (millimeters of mercury) is expressed verbally as "120 over 80." Normal blood pressure is less than 120 mmHg systolic and less than 80 mmHg diastolic.

What Are High Blood Pressure and

Pre hypertension?

Blood pressure is the force of blood against the walls of arteries. Blood pressure rises and falls during the day. When blood pressure stays elevated over time, it is called high blood pressure. The medical term for high blood pressure is hypertension. High blood pressure is dangerous because it makes the heart work too hard and contributes to atherosclerosis (hardening of the arteries). It increases the risk of heart disease and stroke, which are the first- and third-leading causes of death among Americans. High blood pressure also can result in other conditions, such as congestive heart failure, kidney disease, and blindness. A blood pressure level of 140/90 mmHg or higher is considered high. About two-thirds of people over age 65 have high blood pressure. If your blood pressure is between 120/80 mmHg and 139/89 mmHg, then you have pre hypertension. This means that you don't have high blood pressure now but are likely to develop it in the future. You can take steps to prevent high blood pressure by adopting a healthy lifestyle. Those who do not have high blood pressure at age 55 face a 90 percent chance of developing it during their lifetimes. So high blood pressure is a condition that most people have at some point in their lives. Both numbers in a blood pressure test are important, but for people who are 50 or older, systolic pressure gives the most accurate diagnosis of high blood pressure. Systolic pressure is the top number in a blood pressure reading. It is high if it is 140 mmHg or above. What is systolic blood pressure? Systolic pressure is the force of blood in the arteries as the heart beats. It is shown as the top number in a blood pressure reading. High blood pressure is 140 and higher for systolic pressure. Diastolic pressure does not need to be high for you to have high blood pressure. When that happens, the condition is called "isolated systolic hypertension," or ISH. Is isolated systolic high blood pressure common? Yes. It is the most common form of high blood pressure for older Americans. For most Americans, systolic blood pressure increases with age, while diastolic increases until about age 55 and then declines. About 65 percent of hypertensives over age 60 have ISH. You may have ISH and feel fine. As with other types of high blood pressure, ISH often causes no symptoms. To find out if you have ISH — or any type of high blood pressure — see your doctor and have a blood pressure test. The test is quick and painless. Is isolated systolic high blood pressure dangerous? Any form of high blood pressure is dangerous if not properly treated. Both numbers in a blood pressure test are important, but, for some, the systolic is especially meaningful. That's because, for those persons middle aged and older, systolic pressure gives a better diagnosis of high blood pressure. If left uncontrolled, high systolic pressure can lead to stroke, heart attack, congestive heart failure, kidney damage, blindness, or other conditions. While it cannot be cured once it has developed, ISH can be controlled. Clinical studies have proven that treating a high systolic pressure saves lives, greatly reduces illness, and improves the quality of life. Yet, most Americans do not have their high systolic pressure under control. Does it require special treatment? Treatment options for ISH are the same as for other types of high blood pressure, in which both systolic and diastolic pressures are high. ISH is treated with lifestyle changes and/or medications. The key for any high blood pressure treatment is to bring the condition under proper control. Blood pressure should be controlled to less than 140/90 mmHg. If yours is not, then ask your doctor why. You may just need a lifestyle or drug change, such as reducing salt in your diet or adding a second medication. What is diastolic blood pressure? Diastolic pressure is the force of blood in the arteries as the heart relaxes between beats. It's shown as the bottom number in a blood pressure reading. The diastolic blood pressure has been and remains, especially for younger people, an important hypertension number. The higher the diastolic blood pressure the greater the risk for heart attacks, strokes and kidney failure. As people become older, the diastolic pressure will begin to decrease and the systolic blood pressure begins to rise and becomes more important. A rise in systolic blood pressure will also increase the chance for heart attacks, strokes, and kidney failure. Your physician will use both the systolic and the diastolic blood pressure to determine your blood pressure category and appropriate prevention and treatment activities.

Why Is High Blood Pressure Important? High blood pressure is dangerous because it makes the heart work too hard. It also makes the walls of the arteries hard. High blood pressure increases the risk for heart disease and stroke, the first- and third-leading causes of death for Americans. High blood pressure can also cause other problems, such as heart failure, kidney disease, and blindness.

Effect of High Blood Pressure on Your Body Find out about the effect of high blood pressure on your body. Click on the brain, eyes, arteries, kidneys, and heart to get a closer look at what high blood pressure does to these organs.

High blood pressure is the most important risk factor for stroke. Very high pressure can cause a break in a weakened blood vessel, which then bleeds in the brain. This can cause a stroke. If a blood clot blocks one of the narrowed arteries, it can also cause a stroke. Impaired Vision High blood pressure can eventually cause blood vessels in the eye to burst or bleed. Vision may become blurred or otherwise impaired and can result in blindness. Arteries As people get older, arteries throughout the body "harden," especially those in the heart, brain, and kidneys. High blood pressure is associated with these "stiffer" arteries. This, in turn, causes the heart and kidneys to work harder. Arteries As people get older, arteries throughout the body "harden," especially those in the heart, brain, and kidneys. High blood pressure is associated with these "stiffer" arteries. This, in turn, causes the heart and kidneys to work harder. Kidney Damage The kidneys act as filters to rid the body of wastes. Over time, high blood pressure can narrow and thicken the blood vessels of the kidneys. The kidneys filter less fluid, and waste builds up in the blood. The kidneys may fail altogether. When this happens, medical treatment (dialysis) or a kidney transplant may be needed. Heart Attack High blood pressure is a major risk factor for heart attack. The arteries bring oxygen-carrying blood to the heart muscle. If the heart cannot get enough oxygen, chest pain, also known as "angina," can occur. If the flow of blood is blocked, a heart attack results. Congestive Heart Failure High blood pressure is the number one risk factor for congestive heart failure (CHF). CHF is a serious condition in which the heart is unable to pump enough blood to supply the body's needs.

ECG: Reading the Waves

An electrocardiogram (ECG), seen on the right, represents movement of electrical current (depicted in green) through the heart during a heartbeat. The first wave of the ECG, designated P, represents initiation of the heartbeat in the upper chambers of the heart (atria); the QRS complex represents movement of the electrical current through the lower chambers of the heart (ventricles); and the T wave represents the recovery phase, in which the electrical current spreads back over the ventricles in the opposite direction. The heart, seen on the left, is beating in time with the ECG. Oxygen-depleted (blue) blood is pumped from the heart to the lungs, which supply oxygen; oxygen-enriched (red) blood returns from the lungs to the heart and is pumped throughout the body.

I. The Standard 12 Lead ECG

Frank G. Yanowitz, MD Professor of Medicine University of Utah School of Medicine

The standard 12-lead electrocardiogram is a representation of the heart's electrical activity recorded from electrodes on the body surface. This section describes the basic components of the ECG and the lead system used to record the ECG tracings. Topics for study: 1. ECG Waves and Intervals 2. Spatial Orientation of the 12 Lead ECG

1. ECG Waves and Intervals: What do they mean?

 P wave: the sequential activation (depolarization) of the right and left atria

 QRS complex: right and left ventricular depolarization (normally the ventricles are activated simultaneously)

 ST-T wave: ventricular re polarization

 U wave: origin for this wave is not clear - but probably represents "after depolarizations" in the ventricles

 PR interval: time interval from onset of atrial depolarization (P wave) to onset of ventricular depolarization (QRS complex)

 QRS duration: duration of ventricular muscle depolarization

 QT interval: duration of ventricular depolarization and repolarization

 RR interval: duration of ventricular cardiac cycle (an indicator of ventricular rate)

 PP interval: duration of atrial cycle (an indicator or atrial rate)

2. Orientation of the 12 Lead ECG It is important to remember that the 12-lead ECG provides spatial information about the heart's electrical activity in 3 approximately orthogonal directions:

 Right	 	Left
 Superior	 	Inferior
 Anterior	 	Posterior

Each of the 12 leads represents a particular orientation in space, as indicated below (RA = right arm; LA = left arm, LF = left foot):

 Bipolar limb leads (frontal plane): 
 Lead I: RA (-) to LA (+) (Right Left, or lateral)

 Lead II: RA (-) to LF (+) (Superior Inferior)

 Lead III: LA (-) to LF (+) (Superior Inferior)

 Augmented unipolar limb leads (frontal plane): 
 Lead aVR: RA (+) to [LA & LF] (-) (Rightward)

 Lead aVL: LA (+) to [RA & LF] (-) (Leftward)

 Lead aVF: LF (+) to [RA & LA] (-) (Inferior)

 Unipolar (+) chest leads (horizontal plane):
 Leads V1, V2, V3: (Posterior Anterior)

 Leads V4, V5, V6:(Right Left, or lateral)

Behold: Einthoven's Triangle! Each of the 6 frontal plane leads has a negative and positive orientation (as indicated by the '+' and '-' signs). It is important to recognize that Lead I (and to a lesser extent Leads aVR and aVL) are right Ûleft in orientation. Also, Lead aVF (and to a lesser extent Leads II and III) are superior Ûinferior in orientation. The diagram below further illustrates the frontal plane hookup.

LOCATION OF CHEST ELECTRODES IN 4TH AND 5TH INTERCOSTAL SPACES:

V1: right 4th intercostal space

V2: left 4th intercostal space V3: halfway between V2 and V4 V4: left 5th intercostal space, mid-clavicular line V5: horizontal to V4, anterior axillary line V6: horizontal to V5, mid-axillary line

II. A "Method" of ECG Interpretation

Frank G. Yanowitz, MD Professor of Medicine University of Utah School of Medicine

This "method" is recommended when reading all 12-lead ECG's. Like the physical examination, it is desirable to follow a standardized sequence of steps in order to avoid missing subtle abnormalities in the ECG tracing, some of which may have clinical importance. The 6 major sections in the "method" should be considered in the following order: 1. Measurements 2. Rhythm Analysis 3. Conduction Analysis 4. Waveform Description 5. Ecg Interpretation 6. Comparison with Previous ECG (if any)

1. Measurements (usually made in frontal plane leads):

 Heart rate (state atrial and ventricular, if different)

 PR interval (from beginning of P to beginning of QRS)

 QRS duration (width of most representative QRS)

 QT interval (from beginning of QRS to end of T)

 QRS axis in frontal plane (go to: "How To Determine Axis")

Go to: ECG Measurement Abnormalities (Lesson IV) for description of normal and abnormal measurements

2. Rhythm Analysis

 State basic rhythm (e.g., "normal sinus rhythm", "atrial fibrillation", etc.)

 Identify additional rhythm events if present (e.g., "PVC's", "PAC's", etc)

 Consider all rhythm events from atria, AV junction, and ventricles

Go to: ECG Rhythm Abnormalities (Lesson V) for description of arrhythmias

3. Conduction Analysis

 "Normal" conduction implies normal sino-atrial (SA), atrio-ventricular (AV), and intraventricular (IV) conduction. 

 The following conduction abnormalities are to be identified if present:
   SA block (lesson VI): 2nd degree (type I vs. type II)

 AV block (lesson VI): 1st, 2nd (type I vs. type II), and 3rd degree

 IV blocks (lesson VI): bundle branch, fascicular, and nonspecific blocks

 Exit blocks: blocks just distal to ectopic pacemaker site

(Go to ECG Conduction Abnormalities (Lesson VI) for a description of conduction abnormalities)

4. Wave form Description

 Carefully analyze the 12-lead ECG for abnormalities in each of the waveforms in the order in which they appear: P-waves, QRS complexes, ST segments, T waves, and... Don't forget the U waves. 
 P waves (lesson VII): are they too wide, too tall, look funny (i.e., are they ectopic), etc.?

 QRS complexes: look for pathologic Q waves (lesson IX), abnormal voltage (lesson VIII), etc.

 ST segments (lesson X): look for abnormal ST elevation and/or depression.

 T waves (lesson XI): look for abnormally inverted T waves.

 U waves (lesson XII): look for prominent or inverted U waves.

5. ECG Interpretation

 This is the conclusion of the above analyses. Interpret the ECG as "Normal", or "Abnormal". Occasionally the term "borderline" is used if unsure about the significance of certain findings. List all abnormalities. Examples of "abnormal" statements are: 
 Inferior MI, probably acute

 Old anteroseptal MI

 Left anterior fascicular block (LAFB)

 Left ventricular hypertrophy (LVH)

 Nonspecific ST-T wave abnormalities

 Any rhythm abnormalities

Example :

Left Anterior Fascicular Block (LAFB)-KH Frank G.Yanowitz, M.D. HR=72bpm; PR=0.16s; QRS=0.09s; QT=0.36s; QRS axis = -70o (left axis deviation)

Normal sinus rhythm; normal SA and AV conduction; rS in leads II, III, aVF

Interpretation: Abnormal ECG: 1)Left anterior fascicular block

7. Comparison with previous ecg :

 If there is a previous ECG in the patient's file, the current ECG should be compared with it to see if any significant changes have occurred. These changes may have important implications for clinical management decisions.

III. Characteristics of the Normal ECG

Frank G. Yanowitz, MD Professor of Medicine University of Utah School of Medicine

It is important to remember that there is a wide range of normal variability in the 12 lead ECG. The following "normal" ECG characteristics, therefore, are not absolute. It takes considerable ECG reading experience to discover all the normal variants. Only by following a structured "Method of ECG Interpretation" (Lesson II) and correlating the various ECG findings with the particular patient's clinical status will the ECG become a valuable clinical tool. Topics for Study: 1. Measurements 2. Rhythm 3. Conduction 4. Waveform description

1. Measurements

 Heart Rate: 60 - 90 bpm 
 How to calculate the heart rate on ECG paper

 PR Interval: 0.12 - 0.20 sec

 QRS Duration: 0.06 - 0.10 sec

 QT Interval (QTc < 0.40 sec) 
 Bazett's Formula: QTc = (QT)/SqRoot RR (in seconds)

 Poor Man's Guide to upper limits of QT: For HR = 70 bpm, QT<0.40 sec; for every 10 bpm increase above 70 subtract 0.02 sec, and for every 10 bpm decrease below 70 add 0.02 sec. For example: 
 QT < 0.38 @ 80 bpm

 QT < 0.42 @ 60 bpm

Frontal Plane QRS Axis: +90 o to -30 o (in the adult)

2. Rhythm:

       Normal sinus rhythm

The P waves in leads I and II must be upright (positive) if the rhythm is coming from the sinus node.

3. Conduction: Normal Sino-atrial (SA), Atrio-ventricular (AV), and Intraventricular (IV) conduction

Both the PR interval and QRS duration should be within the limits specified above.

4. Waveform Description:

(Normal ECG is shown below - Compare its waveforms to the descriptions below)

   Click to view 
 P Wave

It is important to remember that the P wave represents the sequential activation of the right and left atria, and it is common to see notched or biphasic P waves of right and left atrial activation.

 P duration < 0.12 sec

 P amplitude < 2.5 mm

 Frontal plane P wave axis: 0o to +75o

 May see notched P waves in frontal plane

 QRS Complex

The QRS represents the simultaneous activation of the right and left ventricles, although most of the QRS waveform is derived from the larger left ventricular musculature.

 QRS duration < 0.10 sec

 QRS amplitude is quite variable from lead to lead and from person to person. Two determinates of QRS voltages are: 
 Size of the ventricular chambers (i.e., the larger the chamber, the larger the voltage)

 Proximity of chest electrodes to ventricular chamber (the closer, the larger the voltage)

 Frontal plane leads: 
 The normal QRS axis range (+90 o to -30 o ); this implies that the QRS be mostly positive (upright) in leads II and I.

 Normal q-waves reflect normal septal activation (beginning on the LV septum); they are narrow (<0.04s duration) and small (<25% the amplitude of the R wave). They are often seen in leads I and aVL when the QRS axis is to the left of +60o, and in leads II, III, aVF when the QRS axis is to the right of +60o. Septal q waves should not be confused with the pathologic Q waves of myocardial infarction.

 Precordial leads: (see Normal ECG) 
 Small r-waves begin in V1 or V2 and progress in size to V5. The R-V6 is usually smaller than R-V5.

 In reverse, the s-waves begin in V6 or V5 and progress in size to V2. S-V1 is usually smaller than S-V2.

 The usual transition from S>R in the right precordial leads to R>S in the left precordial leads is V3 or V4.

 Small "septal" q-waves may be seen in leads V5 and V6.

 ST Segment and T wave

In a sense, the term "ST segment" is a misnomer, because a discrete ST segment distinct from the T wave is usually absent. More often the ST-T wave is a smooth, continuous waveform beginning with the J-point (end of QRS), slowly rising to the peak of the T and followed by a rapid descent to the isoelectric baseline or the onset of the U wave. This gives rise to an asymmetrical T wave. In some normal individuals, particularly women, the T wave is symmetrical and a distinct, horizontal ST segment is present.

The normal T wave is usually in the same direction as the QRS except in the right precordial leads. In the normal ECG the T wave is always upright in leads I, II, V3-6, and always inverted in lead aVR.

Normal ST segment elevation: this occurs in leads with large S waves (e.g., V1-3), and the normal configuration is concave upward. ST segment elevation with concave upward appearance may also be seen in other leads; this is often called early repolarization, although it's a term with little physiologic meaning (see example of "early repolarization" in leads V4-6): 

   Click to view

Convex or straight upward ST segment elevation (e.g., leads II, III, aVF) is abnormal and suggests transmural injury or infarction: 

   Click to view

ST segment depression is always an abnormal finding, although often nonspecific (see ECG below): 

   Click to view

ST segment depression is often characterized as "upsloping", "horizontal", or "downsloping". 

   Click to view

  The normal U Wave: (the most neglected of the ECG waveforms) 
 U wave amplitude is usually < 1/3 T wave amplitude in same lead

 U wave direction is the same as T wave direction in that lead

 U waves are more prominent at slow heart rates and usually best seen in the right precordial leads.

 Origin of the U wave is thought to be related to afterdepolarizations which interrupt or follow repolarization.