PHA618 LEC: Heart

• Heart Conducting System

  • network of nodes, cells, and signals that control the heartbeat
  • intiate and transmit electrical impulses responsible for the coordination and contraction of each cardiac cycle
  • responsible for the coordinate contraction of ventricles and atria
• The following are involved in the conduction system:

  • Sinoatrial node
  • atrioventricular node
  • atrioventricular bundle
  • right and left branches
  • purkinje fibers
• arrhythmia


  this is a problem of the electrical signals in the heart
• The electrical activity of the heart can be recorded on the skin's surface using electrodes positioned on the limbs and chest.
• Electrocardiogram

  • shows the spread of electrical signals generated by the SA node as it travels through the atria, AV node, to bundle of His to the right and left bundle branches to the Purkinje fibers.
  • very important in detection of myocardial infarction or ischemia
• P wave


  depolarization of atria (atria squeeze)
• PR interval


  delay of the av node to allow filling of ventricles
• QRS Wave


  depolarization of ventricles (ventricle pumps)
• ST Segment


  beginning of ventricular repolarization, should be flat
• T wave


  ventricles relax (ventricular repolarization)
• Systole


  contraction of ventricles and atria
• Diastole


  relaxation of ventricles and atria
• Heart Failure

  • heart is unable to circulate sufficient blood to meet the needs of the body
  • blood supply is not enough
• Possible causes of heart failure

  • systolic dysfunction
  • diastolic dysfunction
• Systolic dysfunction

  • contraction
  • ventricles do not contract properly
  • ventricles pup out less than 40-50% of the blood
• Diastolic dysfunction

  • there is problem with filling
  • ventricles are stiff; therefore it fills with less blood than normal
  • relaxation
• Right-sided heart failure

  • congestion of peripheral tissue
  • right ventricles does not contract properly going to the lungs; causing congestion/backflow of blood to the peripheral tissue since naipon sa ventricle yung blood
• Left-sided heart failure

  • insufficient pumping of blood to the different parts of the body
  • can causes the blood to remain in the lungs, causing a pulmonary congestion
• Pulmonary edema


  respiratory symptom, cough, paroxysmal nocturnal dyspnea
• Cyanosis and signs of hypoxia


  there is impaired gas exchange because the blood was not able to circulate properly in the lungs
• Decreased cardiac output


  due to the improper contraction of ventricles
• Stenosis

  • narrowing of valve opening
  • low blood flows through the LA to the LV, since there is narrowing of the blood
• Regurgitation

  • failure of a valve to close completely
  • there is backflow because the valve does not close properly
• Ischaemic heart disease

  • also called the coronary heart/artery disease
  • heart is not getting enough blood and oxygen
  • common causes is atheromatous plaque
• Angina Pectoris


  chest pain or discomfort which happens when your heart does not get enough oxygen-rich blood
• Myocardial Infarction


  complete blockage of the artery
• Rheumatic heart disease

  • starts with rheumatic fever is an inflammatory illness that sometimes follows streptococcal throat infections usually in children and young adults
  • an autoimmune disorder
• Cardiac arrhythmia 


  it is any disorder of the heart rate or rhythm and is the result of abnormal generation or conduction of impulses
• Normal sinus rhythm


  60-100 bpm
• Sinus bradycardia


  below 60 bpm
• Sinus tachycardia


  above 100 bpm
• asystole


  No electrical activity in the ventricles and, therefore, no cardiac output. ECG shows flatline
• Fibrillation


  disorderly and uncoordinated contraction of the cardiac muscle fibers
• Atrial fibrillation


  atrial pumping is ineffective and stimulation of the AV node is irregular
• Ventricular fibrillation


  due to the chaotic/uncoordinated pumping activity of ventricles, it can lead to cardiac arrest
• heart block


  occurs when normal impulse transmission is blocked or impaired