Heart Disease 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  Transformation 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 ©

 P wave: atria depolarize (contract releasing the ions)  QRS complex: ventricles depolarize –Spike appears because there are many more heart cells depolarizing  T wave: repolarization of the ventricles –Getting ready for the next heartbeat

 PQRS: indicate systole  T: indicates diastole

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 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  Heart diagram on board

 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  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 die 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

 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

Implanted Defibrillator

 For severe arrhythmias a pacemaker with a defibrillator may be implanted.

Long QT Syndrome

Ruptured Septum after MI ©

For MI Lab Normal Heart Tissue

3 Days After MI

Normal vs. Infarction

Vocabulary  Intercellular spaces:  Edema:  Leukocytes:

Vocabulary  Metaplasia:  Ischemia:  Infarction: