Case 3 (Aj Kanjana) Konan, a ten-year-old intact male Poodle, was admitted to a veterinary hospital with signs of panting and exhaustion. Today, he was panting with mouth breathing before collapsing for 1-2 minutes. On physical examination, Konan was dyspnea with mouth breathing and panting. The frothy exudate from his nostril was observed. His mucous membrane was cyanosis. His heart rate was 180 beats per minute. Auscultation of thorax revealed heart murmur in the mitral valve area; crackles were heard in the lungs. Abdominal palpation was unremarkable. Problem list : Respiratory system Cardiovascular system Nervous system Dyspnea : mouth breathing and panting Cyanosis Dyspnea : mouth breathing and panting Frothy exudate from his nostril Crackles in the lungs Tachycardia (HR : 180 bpm) Crackles in the lungs Heart murmur at mitral valve Cardiovascular system Anatomy of the heart Picture 1 : The anatomy of the heart includes four chambers ( References : https://my.clevelandclinic.org/health/body/21704-heart ) the parts of the heart ● Walls. ● Chambers that are like rooms. ● Valves that open and close like doors to the rooms. ● Blood vessels like plumbing pipes that run through a building. ● An electrical conduction system like electrical power that runs through a building. Heart walls Heart walls are the muscles that contract (squeeze) and relax to send blood throughout the body. A layer of muscular tissue called the septum divides heart walls into the left and right sides. heart walls have three layers: 1. Endocardium: Inner layer. 2. Myocardium: Muscular middle layer. 3. Epicardium: Protective outer layer. The epicardium is one layer of pericardium. The pericardium is a protective sac that covers the entire heart. It produces fluid to lubricate the heart and keep it from rubbing against other organs. Heart chambers Dog’s heart has four separate chambers. have two chambers on the top (atrium, plural atria) and two on the bottom (ventricles), one on each side of the heart. ● Right atrium: Two large veins deliver oxygen-poor blood to the right atrium. The superior vena cava carries blood from the upper body. The inferior vena cava brings blood from the lower body. Then the right atrium pumps the blood to the right ventricle. ● Right ventricle: The lower right chamber pumps the oxygen-poor blood to lungs through the pulmonary artery. The lungs reload the blood with oxygen. ● Left atrium: After the lungs fill blood with oxygen, the pulmonary veins carry the blood to the left atrium. This upper chamber pumps the blood to the left ventricle. ● Left ventricle: The left ventricle is slightly larger than the right. It pumps oxygen-rich blood to the rest of the body. Heart valves Dog’s heart valves are like doors between heart chambers. They open and close to allow blood to flow through. They also keep blood from moving in the wrong direction. Atrioventricular valves The atrioventricular (AV) valves open between upper and lower heart chambers. They include: ● Tricuspid valve: Door between right atrium and right ventricle. ● Mitral valve: Door between left atrium and left ventricle. Semilunar valves Semilunar (SL) valves open when blood flows out of ventricles. They include: ● Aortic valve: Opens when blood flows out of the left ventricle to the aorta (artery that carries oxygen-rich blood to body). ● Pulmonary valve: Opens when blood flows from the right ventricle to pulmonary arteries (the only arteries that carry oxygen-poor blood to lungs). Blood vessels heart pumps blood through three types of blood vessels: ● Arteries carry oxygen-rich blood from heart to body’s tissues. The exception is ● pulmonary arteries, which go to the lungs. Veins carry oxygen-poor blood back to the heart. ● Capillaries are small blood vessels where the body exchanges oxygen-rich and oxygen-poor blood. Electrical conduction system Picture 2 : Diagram of the cardiac conduction system ( References : https://my.clevelandclinic.org/health/body/21704-heart ) The heart's conduction system is like the electrical wiring of a building. It controls the rhythm and pace of the heartbeat. Signals start at the top of the heart and move down to the bottom. Dog’s conduction system includes: ● Sinoatrial (SA) node: Sends the signals that make the heart beat. Atrioventricular (AV) node: Carries electrical signals from heart’s upper chambers to its lower ones. ● Left bundle branch: Sends electric impulses to the left ventricle. ● Right bundle branch: Sends electric impulses to the right ventricle. ● Bundle of His: Sends impulses from AV nodes to the Purkinje fibers. Purkinje fibers: Make heart ventricles contract and pump out blood. ● ● Auscultation structure Dogs Mitral valve L,5th ICS at CCJ Aortic valve L,4th ICS above CCJ Pulmonic valve L,2nd-4th ICS at CCJ just above the sternum Tricuspid valve R,3rd-5th ICS at CCJ ICS = intercostal space L = left CCJ = costochondral junction R = right Picture 3 : Diagram showing approximate valve locations for auscultation (copyright J.M. Naylor 2001 University of Saskatchewan) (References : https://www.vetvisions.com/small-animal-cardiology-auscultation/ ) Mitral Regurgitation ; pathogenesis and clinical finding 1. If mitral regurgitation occurs while the left ventricle is systolic, some blood will flow back to the left atrium, increasing volume and pressure in the left atrium. Later, when the left ventricle is diastolic, the blood from the left atrium will be sent to the left ventricle, causing increased volume to push back into the left ventricle. At this time, it will cause S3 heart sound, which is the sound caused by rapid ventricular filling. When the blood enters the left ventricle more than normal, the heart will expand to support more blood, which causes eccentric left ventricular hypertrophy. Picture 4 : Mitral regurgitation (References : https://www.mayoclinic.org/diseases-conditions/mitral-valveregurgitation/symptoms-causes/syc-20350178) 2. Apical impulse, also known as the point of maximal impulse (PMI) and the apex beat, is the pulse point on the chest at the point over the apex of the heart. It is different from the other pulse. When palpation, another pulse point located in the arteries throughout the body senses the heart rate, while apical impulse, palpated in the mitral area in dogs, senses the contraction of the left ventricle that pumps blood from the heart through the aorta to the rest of the body. Apical impulse on palpation and auscultation is one of the clinical findings that provide many contents such as heart rhythm or the strength of pulse directly to the left ventricle. Therefore, apical pulse is the most accurate reading of heart rate and it can indicate heart health. 3. The consequences associated with common cardiac defects, mitral regurgitation. With each contraction of the left ventricle, a normal volume of blood is ejected into the aorta, and an additional volume of blood is ejected backward (through the regurgitant valve) into the left atrium. As a result, there is an increase in the volume work performed by the left ventricle. Therefore mild-to-moderate left ventricular hypertrophy develops. Also, in a heart with mitral regurgitation, the left atrium becomes distended, and left atrial pressure increases, as does pulmonary venous pressure. Elevated pressure in the pulmonary blood vessels forces water and electrolytes out of the bloodstream and into the pulmonary interstitial space, causing pulmonary edema. In the lung, as in other organs, there is continual movement of water and solutes from the capillary bed into the lung interstitium. Forces describes in starling's equation govern the movement of fluid across the pulmonary capillary endothelium as follows: 𝐹𝑙𝑢𝑖𝑑 𝑖𝑛𝑓𝑙𝑢𝑥 = 𝐾{(𝑃𝑐𝑎𝑝 − 𝑃𝑖𝑓) − 𝜎(𝛱𝑐𝑎𝑝 − 𝛱𝑖𝑓)} Where 𝐾 is the rate of flow (mL/h) per unit of pressure across the endothelium and is referred to as the filtration coefficient; 𝑃𝑐𝑎𝑝 is capillary hydrostatic pressure; 𝑃𝑖𝑓 is interstitial fluid hydrostatic pressure; 𝛱𝑐𝑎𝑝 and 𝛱𝑖𝑓 are capillary and interstitial colloid osmotic (oncotic) pressure respectively; and 𝜎 is the reflection coefficient,which indicates how effective the capillary endothelium is at preventing the movement of proteins and other solutes. When the normal values shown in picture 5 are inserted into Starling’s equation, the net force is positive and favors fluid filtration out of the capillaries and into the interstitium. Picture 5 : Diagrammatic representation of a pulmonary capillary in the alveolar septum. Top, on the “thin” side of the septum, capillary endothelium and alveolar epithelium share a basement membrane. Bottom, on the “thick” side of the septum, endothelium and epithelium are separated by a layer of interstitial tissue. Typical values for capillary and interstitial fluid hydrostatic pressures (𝑃𝑐𝑎𝑝 and 𝑃𝑖𝑓) and oncotic pressures (𝛱𝑐𝑎𝑝 and 𝛱𝑖𝑓) are shown. (Reference: Klein BG: Cunningham’s Textbook of Veterinary Physiology, 6th ed.,2020,p 572) Increases in capillary hydrostatic pressure occur in animals with left-sided heart failure. These elevated pressures result in an increased fluid influx into the interstitium. As fluid transfer out of capillaries increase even further, excess fluid accumulates around the bronchi and large vessels in the compliant peribronchial and perivascular spaces. Fluid flux across the pulmonary capillary endothelium, the proteoglycan bridge in the alveolar septum break, which greatly allows greater fluid movement into the interstitium. This fluid is termed pulmonary interstitial edema and is seen radiographically as peribronchial cuffing. Picture 6: Peribronchial cuffing refers to a radiographic term used to describe haziness or increased density around the walls of a bronchus or large bronchiole. (Reference: https://www.teachingmedicine.com/tutorial/CHF/Peribronchial_cuffing ) When fluid pressure within pulmonary interstitium exceeds the barrier capacity of the alveolar epithelium,the clinically evident alveolar edema occurs as fluid enters the air spaces across the alveolar epithelial cells or at the level of the bronchioles . Picture 6: The development of pulmonary interstitial edema and alveolar edema (Reference:https://www.semanticscholar.org/paper/Diagnosis-and-management-ofcardiogenic-pulmonary-Alwi/9a1c410cfb48e56ea1b28447473758966988a799) Pulmonary edema may cause crackling sounds in your lungs. People or animals with congestive heart failure (CHF) often have pulmonary edema. CHF occurs when the heart cannot pump blood effectively. This results in a backup of blood, which increases blood pressure and causes fluid to collect in the air sacs in the lungs. 4.Mitral regurgitation is incompetency of the mitral valve causing flow from the left ventricle into the left atrium during ventricular systole. This leads to a reduction in stroke volume ejected into the aorta, resulting in decreased cardiac output, causing insufficient blood to supply various organs.When there is not enough blood flowing to the organs, it stimulates the The renin-angiotensin-aldosterone system (RAAS) .RAAS is the system of hormones, proteins, enzymes and reactions that regulate blood pressure and blood volume on a longterm basis. It regulates blood pressure by increasing sodium (salt) reabsorption, water reabsorption (retention) by kidney and vascular tone (the degree to which blood vessels constrict, or narrow) leading to an increase in intravascular hydrostatic pressure systemically. This causes water to be driven out of the blood vessels into the interstitial space, resulting in peripheral edema. The renin-angiotensin-aldosterone system (RAAS) The first stage of the RAAS is the release of the enzyme renin. Renin released from granular cells of the renal juxtaglomerular apparatus (JGA) in response to one of three factors: ● Reduced sodium delivery to the distal convoluted tubule detected by macula densa cells. ● Reduced perfusion pressure in the kidney detected by baroreceptors in the afferent arteriole. ● Sympathetic stimulation of the JGA via β1 adrenoreceptors. Angiotensinogen is a precursor protein produced in the liver and cleaved by renin to form angiotensin I. Angiotensin I is then converted to angiotensin II by angiotensin converting enzyme (ACE). This conversion occurs mainly in the lungs. Angiotensin II exerts its action by binding to various receptors throughout the body. The table below outlines its effect at different points. Site Main Action Arterioles Vasoconstriction Kidney Stimulates Na+ reabsorption Sympathetic nervous system Increased release of noradrenaline (NA) Adrenal cortex Stimulates release of aldosterone Hypothalamus Increases thirst sensation and stimulates antidiuretic hormone (ADH) release 5. Blood consistently flows backward throughout the systole, resulting in Holosystolic murmur at mitral valve which is to hear the murmur throughout the compression period. And it usually Radiates to the axilla. In addition, the amount of blood that goes to the body decreases or the stock volume decreases so the heart muscle has to contract more. Therefore, increase afterload. 6. The serum creatinine is increased. Creatinine is the wasted product in metabolism of protein and the beaking down of muscular tissue. Due to the decreased cardiac output cause the decreasing amount of oxygen to the kidney, this lead to renal dysfunction. The kidney parenchyma are injured due to oxygen insufficient which result in decreasing of Glomerula filtration rate (GFR) and ability of kidney to clear out creatinine. Nervous system The nervous system includes the brain, spinal cord, and a complex network of nerves. This system sends messages back and forth between the brain and the body. The brain is what controls all the body's functions. The spinal cord runs from the brain down through the back. It contains threadlike nerves that branch out to every organ and body part. This network of nerves relays messages back and forth from the brain to different parts of the body. The nervous system is made up of the central nervous system and the peripheral nervous system: The central nervous system includes the brain and spinal cord. ● The peripheral nervous system includes the nerves that run throughout the whole body. The nervous system uses tiny cells called neurons to send messages back and forth from the brain, through the spinal cord, to the nerves throughout the body. ● Billions of neurons work together to create a communication network. Different neurons have different jobs. For example, sensory neurons send information from the eyes, ears, nose, tongue, and skin to the brain. Motor neurons carry messages away from the brain to the rest of the body to allow muscles to move. These connections make up the way we think, learn, move, and feel. They control how our bodies work — regulating breathing, digestion, and the beating of our hearts. The CNS The CNS (Central Nervous System) components involved in regulating the heart and lungs Hypothalamus The hypothalamus is a crucial region of the brain located below the thalamus, forming the floor of the third cerebral ventricle. It's a small, cone-shaped structure that extends downward from the brain, terminating in the pituitary stalk, which connects it to the pituitary gland. Functionally, the hypothalamus serves as a control center for numerous autonomic nervous system functions and interacts intricately with the endocrine system through its connections with the pituitary gland. The brainstem The brainstem, located in the middle of the brain, is the stalk-like part of the brain that connects the brain to the spinal cord and is only about one inch long. This region regulates essential functions such as blood pressure, breathing, heart rhythms, and swallowing. The brainstem can be further subdivided into the midbrain, pons, and medulla. The midbrain, otherwise known as the mesencephalon, is crucial for regulating eye movements, emotions, hearing, and long-term memory. Notably, the substantia nigra, rich in dopamine neurons, is located within the midbrain and is often affected by Parkinson's disease. The pons is the starting location for four of the 12 cranial nerves. Some of the different functions regulated by the pons include facial movements, hearing, breathing, and balance. The medulla is located at the bottom of the brainstem where the brain and spinal cord meet. This region of the brainstem regulates breathing, heart rate, and blood pressure. Additionally, the medulla maintains reflective activities such as sneezing, vomiting, coughing, and swallowing. The PNS The PNS consists of both the somatic and autonomic nervous systems. Taken together, these systems transmit information from different areas of the body to the brain and ensure that signals sent from the brain are transmitted to other areas of the body. (Reference : https://en.wikivet.net/Autonomic_Nervous_System_-_Anatomy_%26_Physiology) The somatic nervous system The somatic nervous system (SNS) consists of peripheral nerve fibers that carry sensory information or sensations from peripheral organs to the CNS. The SNS also includes motor nerve fibers that exit the brain to carry commands for movement to the skeletal muscles. For example, upon touching a hot object, sensory nerves carry information about the heat to the brain. Subsequently, the brain, through motor nerves, commands the hand muscles to withdraw it immediately. This process takes less than one second to complete. The neural cell body that carries this information often lies within the brain or spinal cord and projects directly to a skeletal muscle. The autonomic nervous system The autonomic nervous system (ANS) controls the nerves of the body's inner organs that cannot be controlled consciously. The ANS can be further subdivided into the sympathetic, parasympathetic, and enteric nervous systems. Some of the different activities controlled by the ANS include the heartbeat, digestion, subconscious breathing, blood pressure, and sexual arousal. (Reference : https://www.pinterest.com/pin/autonomic-nervous-system-nervous-system-ofanimals--263390278180895432/) The sympathetic pathway is associated with the heart and lungs. The sympathetic pathway originating from the medulla➝spinal cord➝preganglionic neurons ➝ middle cervical ganglia➝cardiac plexus and the vagosympathetic trunk➝heart, bronchiole smooth muscle, and blood vessels ➝ heart rate increase dilation of the trachea and bronchi, dilation of bronchioles in the lungs, vasodilation (increasing blood flow in the cardiac muscle), and systemic vasoconstriction. Backward Heart Failure → Mitral Regurgitation (MR) The activation of the sympathetic nervous system (SNS) increases stroke volume by providing inotropic support to the failing heart, while also inducing peripheral vasoconstriction to maintain mean arterial perfusion pressure. Heart Mitral regurgitation (MR)➝cardiac output decreases➝ leading to a drop in blood pressure ➝ Baroreceptor and chemoreceptor reflexes detect➝signaling the hypothalamus and medulla oblongata ➝ activates the sympathetic tone➝increasing sympathetic pathway activity➝heart rate raises ➝tachycardia. Kidney Mitral regurgitation (MR)➝cardiac output decreases ➝ causing a drop in blood pressure ➝ Baroreceptor and chemoreceptor reflexes detected ➝ signaling the hypothalamus and medulla oblongata➝sympathetic tone increase➝activates the Renin-AngiotensinAldosterone System (RAAS). Lungs Mitral regurgitation (MR)➝pulmonary edema ➝ Blood gas abnormality (O2↓ CO2↑) ➝ Chemoreceptors(carotid bodies and medulla oblongata) detected ➝afferent impulses➝the brainstem respiratory center for processing (pons and medulla) ➝generates efferent impulses ➝ resulting in dyspnea. Pulmonary edema can cause disturbances in the airway epithelium➝triggering sensory receptors like the juxtacapillary receptors➝receptors detect➝send afferent impulses➝brainstem, specifically the pons and medulla ➝ efferent impulses ➝ the lungs ➝ leading to dyspnea. Pulmonary edema➝mechanical respiratory load➝increasing airway resistance and elastance➝Mechanoreceptors and chest wall receptors, such as muscle spindles and Golgi tendon organs detected ➝ generating afferent impulses➝brainstem➝The somatosensory cortex processes this information ➝ efferent impulses➝chest wall and diaphragm➝resulting in dyspnea. Respiratory system Frothy exudate In heart failure (HF), pleural effusion results from increased interstitial fluid in the lung due to elevated pulmonary capillary pressure.then plasma will leak to alveolar space and mix with surfactant in the alveolar surface.the mixture of fluid is beated in one direction toward the pharynx by ciliary escalator mechanism.eventually the mixture of fluid is frothy by ciliary movement Dyspnea Dyspnea refers to labored or difficult breathing and is often associated with hypoventilation. A person suffering from dyspnea is aware, or conscious, of the breathing pattern and is generally uncomfortable and in distress. Orthopnea refers to dyspnea while lying down. It is relieved by sitting or standing up. This condition is common in patients with heart disease. 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