1. Homeostatic imbalances
Pericarditis inflammation of the pericardium
Endocarditis bacterial infection of the endocardium can lead to valvular stenosis
Myocardial infarction heart attack/coronary
Heart block any damage to the AV node results in irregular beating of ventricles
Murmurs abnormal or unusual hearts sounds

2. ECG: normal and abnormal

3. Alterations in Electrocardiogram
Clinical Cardiology Concepts for Vets

4. Cardiac Output
Cardiac Output - the amount of blood pumped by a ventricle per minute. Units may be in milliliters or Liters per minute.
Heart Rate - number of cardiac cycles per minute. Average for males = 64-72/min. Average for females = 72-80/min.
Stroke Volume - amount of blood pumped out of a ventricle each beat. Average resting stroke volume = 70 ml.

5. Cardiac Output CO (mL/min) =SV (70 mL/beat) X HR (75 beat/min)
Cardiac output = stroke volume X heart rate = 5250ml/min
SV= EDV - ESV
Stroke volume = end diastolic volume – end systolic volume
Cardiac reserve is the difference between a person’s maximum cardiac output and cardiac output at rest.

6. Frank Starling Law of the Heart
The more cardiac muscle is stretched within physiological limits, the more forcibly it will contract.
Rubber band analogy
Increasing volumes of blood in ventricles increase the stretch & thus the force generated by ventricular wall contraction.
Greater stretch means more blood volume is pumped out, up to physical limits.

7. Regulation of stroke volume
Preload is the degree of stretch on the heart.
Contractility is the force of ventricular contractions.
Afterload is the pressure that must be exceeded to eject blood from the ventricles.
The Frank-Starling law of the heart—preload is the critical factor controlling SV (stroke volume).

8. Regulation of heart rate
When blood volume drops or the heart is weakened, SV drops and the HR increases.
Positive chronotropic factors increase HR.
Negative chronotropic factors decrease HR.
Extrinsic regulation by the ANS
Sympathetic nervous system increases firing of the pacemaker and enhances Ca2+ entry into heart cells.
Parasympathetic nervous system reduces heart rate through ACh which opens K+ channels.
Under resting conditions the PNS is dominant

9. Chemical Regulation Hormones Ions
Epinephrine enhances HR and contractility
Thyroxine enhances effects of Epi and NE and leads to slower more sustained increase in HR
Ions
Hypocalcemia (Ca2+)depresses the heart;
Hypercalcemia prolongs the plateau phase and lead to heart irritability
Hyperkalemia (K+) may lead to heart block and cardiac arrest; hypokalemia leads to arrhythmia and weakened contractions.
Excess Na+ blocks Ca2+ inflow, decreasing contractile strength

10. Other Factors Exercise leads to a reduced HR when at rest.
Working large body muscles for at least 20 minutes elevates cardiac output and accelerates metabolism.
Athletes have a larger heart and a resting HR of beats per minute
Increased temperature increases heart rate; decreased temperatures reduce heart rate and oxygen needs.

11. Homeostatic imbalances
Congestive heart failure
Caused by Coronary artherosclerosis
Caused by  Persistent high blood pressure
Caused by Multiple myocardial infarcts
Left side failure Pulmonary congestion
Rights side failure Peripheral congestion

12. Angina Pectoris
Medical term for chest pain due to coronary heart disease.
It occurs when the myocardium doesn’t get as much blood (Oxygen) as it needs.
Insufficient blood supply is called ischemia.
May initially occur during physical exercise, stress, or extreme temperatures.
It is a sign of increased risk of heart attack.

13. Cardiac Arrhythmias Tachycardia: Heart rate in excess of 100bpm
Arrhythmias irregular heart rhythms that may lead to fibrillation
Tachycardia: Heart rate in excess of 100bpm
Bradycardia: Heart rate less than 60 bpm
Sinus arrhythmia: Heart rate varies 5% during respiratory cycle and up to 30% during deep respiration
Premature atrial contractions: Occasional shortened intervals between one contraction and succeeding, frequently occurs in healthy people

14. Aneurysm
Weakness of the wall of an artery causing an abnormal enlargment or bulge.
The aorta or the arteries that supply the heart, brain, legs or kindeys are most commonly affected.

15. Atherosclerosis (Arteriosclerosis)
Narrowing and hardening of arteries and impairment of blood flow due to the deposition of fatty materials and calcium in their walls.
Risk factors include:
smoking
inactivity
diabetes
high blood cholesterol
personal or family history of heart disease
Atherosclerosis Animation

16. Resources Heart Sounds & Cardiac Arrhythmias Live Cardiac Exam Video
Anatomy Links
Cardiac Cycle
Cardiac Cycle Graphics
Interactive Physiology Review
AP II Notes Homepage

17. Conducting System of Heart