Myocardial Infarction Heart Disease Myocardial Infarction

Myocardial Infarction Heart attack Leading cause of death in the US Usually caused by an occluded vessel Males more often affected until later in life

Assuming the individual survives the MI: 18 to 24 hours: The damaged heart tissue will appear pallor (white in color, not pink) 2 to 4 days: The dead tissue will appear yellow-brown and soft

10 days: Scar tissue forms at the margin of the infarction Called metaplasia

Metaplasia Replacement of one type of mature differential (specialized) cell into another type (due to injury) Scar tissue (fibroblast cells) forms—you can often see the nuclei of these cells

Symptoms: Intense, crushing pain located below the sternum Pain often radiates down left shoulder, arm, or jaw Breathlessness Anxiety Nausea Vomiting Perspiration

Many people do not realize they are having heart attacks Mistake symptoms for indigestion

After the onset of a MI, there may be no obvious problems Or Arrhythmias or pump failure may occur

Before we begin arrhythmias, how does a normal heart function and how does the pattern appear on an EKG?

Each heartbeat originates as an electrical impulse from a small area of tissue in the right atrium: sinus node Impulse is a wave of negative ions

The impulse travels cell by cell to the atrioventricular node —a cluster of cells in the center of the heart (the only electrical connection between the heart chambers) It travels along the Bundle of HIS

The impulse is delayed at the atrioventricular node until the atria fully contract. The atria fully contract before the ventricles are stimulated.

Heart

An EKG consists of 12 leads that can pick up these negative ion waves We mainly focus on only one lead (called lead 2)

Normal Heart Pattern on an EKG ©http://students. med. nyu

P wave: atria depolarize (release of ions and contraction of atria) QRS complex: ventricles depolarize Spike appears because there are many more heart cells depolarizing Release of ions and contraction of ventricles T wave: repolarization of the ventricles Getting ready for the next heartbeat

PQRS: indicate systole T: indicates diastole

http://www.youtube.com/watch?v=lIQXzgesdDg

How would an atrial problem look on an EKG? How would a ventricular problem look on an EKG?

Deep Q Shows an old infarction Person had a MI in the past The deeper the Q, the greater the infarction

Arrhythmia Irregular heartbeat This is what usually kills the individual

The MI acts as an extra pacemaker—releases negative ions

There are different types of arrhythmias Can be seen on an EKG

People die because the cells cannot control these ions, not because of the damage to the heart

Types of Arrhythmias Flutter Mild quivering of atria or ventricles Fibrillation Entire chamber of the heart undergoes quivering with chaotic impulses Can affect the atria or the ventricles

Types of Arrhythmias Atrial fibrillation Atria only pumps approximately 30% of blood into ventricles—the rest “falls out” (churning) Most people survive this Problem? thrombus may form

Thrombus may form

Types of Arrhythmias Most individuals are on an anticoagulant (blood thinner) Usually seen in older people Not typically associated with MIs

Types of Arrhythmias Ventricular fibrillation Very dangerous—why? No blood is really pumping

Types of Arrhythmias On board How would you describe this to a doctor? ST problem —elevated ST segment Very significant problem The heart is in ischemia usually due to a clot

Nicknamed Tombstone Effect Looks like a headstone If you can get the person anti-thrombolic drugs soon enough, he should be okay If not, heart will go into ventricular fibrillation

How do we stop fibrillation? Defibrillate “Knocks” out all of the ions and starts over Person flat lines—heart stops and then restarts itself with a normal pattern

Only use a defibrillator if the person is in fibrillation Can implant a defibrillator into a person’s chest

Types of Arrhythmias PVC: pre-ventricular contraction Has been seen in teenagers, but most outgrow it Not good in older people

Types of Arrhythmias Tachycardia Any heart rate faster than 100 beats/min Brachycardia A slow rhythm, less than 60 beats/min

Treatment for Arrhythmias Treatment: Pacemaker Can speed up the heart, slow down the heart, assist with irregular beating Most pacemakers also have a defibrillator

Implanted Defibrillator

Long QT Syndrome

Ruptured Septum after MI ©http://www-tc. pbs

For MI Lab Normal Heart Tissue

3 Days After MI

Normal vs. Infarction

Vocabulary Intercellular spaces: Edema: Leukocytes:

Vocabulary Metaplasia: Ischemia: Infarction: