Inotropy, Chronotropy, and Dromotropy

• Inotropy refers to the strength of cardiac muscle contraction, while chronotropy refers to heart rate, and dromotropy refers to the rate of nervous impulse conduction.
• The heart uniquely generates its own electrical impulses due to the self-excitation or automaticity of individual cells.
• The cell with the fastest discharge rate within the cardiac system acts as the heart’s primary pacemaker, possessing the highest rate of automaticity.

Possible Symptoms

• Cardiovascular symptoms include cardiac ischemia, pericarditis (viral or autoimmune), and aortic dissection.
• Respiratory symptoms include pulmonary embolism, pneumothorax, pneumonia, and pleurisy (pleural irritation).
• Gastrointestinal (GI) symptoms include cholecystitis, pancreatitis, hiatal hernia, esophageal disease, gastroesophageal reflux disease (GERD), peptic ulcer disease, and dyspepsia.
• Musculoskeletal symptoms include chest wall syndrome, costochondritis, acromioclavicular disease, herpes zoster (shingles), chest wall trauma, and chest wall tumors.
• General signs and symptoms include discomfort, dyspnea, cough, syncope, palpitation, altered level of consciousness (ALOC), diaphoresis, restlessness and anxiety, a feeling of impending doom, nausea/vomiting, fatigue, edema, headache, anguished facial expression, activity limitations, and trauma.
• Diabetic patients with myocardial injury may not exhibit chest pain.

Risk Factors

• Risk factors include smoking, cocaine use, older age, family history of cardiac disease, hypertension, hypercholesterolemia, carbohydrate intolerance, male gender, lack of exercise, diet, obesity, oral contraceptives, Type A personalities, and psychosocial tensions (stress).

Out-of-Hospital Treatment

• Out-of-hospital treatment involves point-of-care (POC) testing, IV fluids, medications (aspirin, nitro, fentanyl, O2), and treatments for accompanying heart rate and rhythm issues (adenosine, lidocaine).
• Other therapies include prescribed medications and lifestyle changes.

Electrical Conduction

• The sinoatrial (SA) node serves as the primary pacemaker with an intrinsic rate of 60-100 bpm.
• The interatrial pathway spreads from the SA node to the left atrium, enabling its contraction.
• The internodal pathway connects the SA node to other electrical junctions.
• The atrioventricular (AV) junction delays the signal, allowing the atria to fully depolarize and contract blood into the ventricles.
• It is the secondary pacemaker, functioning as a backup with an intrinsic rate of 40-60 bpm.
• Signals travel from the AV junction to the Bundle of His, then split into left and right bundle branches, ending finally at the Purkinje fibers.
• Purkinje fibers facilitate ventricular contraction and act as the last backup pacemaker, with an intrinsic rate of 20-40 bpm.
• Irritability occurs when a lower site on the pathway assumes the role of the pacemaker.
• The escape mechanism activates when a lower pacemaker site takes over because the normal pacemaker fails.

Pericarditis

• Pericarditis involves inflammation of the pericardium, leading to swelling and irritation of the heart's surrounding membranous sac.
• The condition typically arises as the inflamed linings rub against each other, resulting in sharp or stabbing pain.
• Heart attacks or heart surgeries can also trigger pericarditis.

Inotropy refers to the strength of cardiac muscle contraction, while chronotropy refers to heart rate, and dromotropy refers to the rate of nervous impulse conduction. The heart uniquely generates its own electrical impulses due to the self-excitation. Cardiovascular symptoms include cardiac ischemia and pericarditis.