BIO202 - Ch 18 - Heart - Marieb/Hoehn - RioSalado - AZ
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| The heart weighs __. | 250 - 350 g - less than a pound.
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| Where is the heart found? | Mediastinum - medial cavity of thorax
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| Heart location in relation to bones? | Heart extends obliquely 12-14 cm (5 inches) from 2nd rib to 5th intercostal space - in mediastinum rest on diaphragm
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| 2/3 mass of heart __. | lies to left of midsternal line.
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| The base of heart points to __ & apex points __. | shoulder (R), left hip
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| Endocardium is comprised of? | Glistening white sheet of endothelium (squamous) resting on thin CT layer - lines heart chambers.
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| The __ is continuous w/the endothelial lining of the blood vessels leaving & entering the heart. | Endocardium - located on inner myocardial surface.
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| Which chamber forms the heart apex? | L-ventricle
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| The muscle bundles on the right atrium anterior. | Pectinate muscles - becuase they look like teeth of a comb.
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| The __ is the spot that marks where opening was in the fetal heart. | Fossa ovalis
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| myocardium | Cardiac muscle tissue
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| pericardium | Tough fibrous sac that surrounds, protects & lubricates the heart.
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| endocardium | Smooth lining in heart's chambers composed of CT & layer of epithelial cells.
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| endothelium | Epithelial cell layer of heart & blood vessels.
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| Septum | Thick wall that divides R & L halves
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| Atrium | Top two heart chambers
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| Ventricle | Bottom two heart chambers
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| Hearth has __ halves & __ chambers. | 2 - 4
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| Atrioventricular Valve | Flaps of membrane separating an atrium & ventricle chamber (R=tri & L=Bi or mitral).
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| Atria are __ for blood returning to heart & contribute __ to the propulsive pumping activity of heart. | Receiving chambers - little
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| Blood enters R atrium via what 3 veins? | Superior vena cava, inferior vena cava, & coronary sinus.
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| What veins enter the L atrium? | The 4 pulmonary veins
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| The __ ventricle forms most of anterior & the __ the posterioinferior. | Right, left
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| The R ventricle pumps blood into the __ while the L ventricle ejects blood into the __. | Pulmonary trunk, aorta
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| The blood vessels that carry blood to/from the lungs form __. | The pulmonary circuit - serves gas exchange
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| The blood vessels that carry functional blood supply to/from tissues __. | The systemic circuit
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| The right side of the heart is the __ circuit pump. | Pulmonary
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| The left side of the heart is the __ circuit pump. | Systemic
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| Path of blood through heart. | RA -> RV -> Lungs -> PV -> LA -> LV -> Aorta
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| The pulmonary circuit served by __ ventricle is a __ pressure circulation. | right - low
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| The systemic circuit served by __ ventricle is a __ pressure circulation. | left - high - that's why left ventricle is bigger.
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| What is the shortest circulation in the body? | The coronary circulation - blood supply to heart.
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| What are anastomoses? | Where blood vessels merge.
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| "Heart strings" / chordae tendineae | Tough, collagen-reinforced strands that connect AV valve flaps to cone-shaped muscles that extend out of ventricle wall.
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| Semilunar valves (aortic & pulmonary) | Valves between the ventricle & arteries leading away from it. During a heartbeat, this valve opens & closes to keep blood moving in one direction. 3 cusps
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| Coronary circulation | Heart's own blood supply. Coronary arteries
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| Coronary arteries | Bring blood to the heart for itself.
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| Aorta | The major artery carrying oxygenated blood away from heart.
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| During a MI, damage to the __ ventricle is most serious. | Left, because it is the systemic pump & cannot handle being replaced by scar tissue.
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| Atrioventricular valves prevent __. | backflow into atria when ventricles contract.
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| The R-AV valve is the __. | Tricuspid - has 3 flexible cusps.
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| The L-AV valve is the __. | MItral - 2 cusps
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| What occurs in valvular stenosis? | Valve flaps become stiff (scar tissue or Ca salt deposit) & constrict opening.
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| "lub" | AV valves are closing as the 2 ventricles contract. Beginning of ventricular systole.
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| "dup" | The semilunar valves are closing as ventricles relax.
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| Superior vena cava | Blood from head, arms & chest arrives to heart through this.
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| Inferior vena cava | Blood from lower body returns to heart through this.
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| What is functional syncytium? | Cardiac cells that are electrically coupled in the myocardium that behave like single coordinated unit.
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| What give cardiac cells a high resistance to fatigue? | Large mitrochondria - 25-35% of volume
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| Cardiac muscles lack __. | triads
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| Each cardiac muscle must be stimulated to __, but some initiate their own depolarization, which is called __. | contract by a nerve cell - automaticity or autorhythmicity
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| The long cardiac refractory period prevents __. | tetanic contractions, which would stop heart pumping action.
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| The plateau of heart cell contraction helps how? | Provides sustained contraction needed to eject blood from heart.
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| Cardiac muscle has more __ than skeletal. | mitochondria - needs more oxygen
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| Cardiac muscle is __ & doesn't depend on NS. | intrinsic - NS can alter basic rhythm
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| Autorhythmic cells don't maintain __. | a stable resting potential
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| intercalcalted discs | Junctions that span heart muscle cell's plasma membrane where 2 cells abutt - connected by desmosomes & gap junctions
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| Cardiac conduction system | Pacemaker cells in the heart that spontaneously generate & conduct electrical impulses - noncontractile cells.
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| Sinoatrial node (SA) | Cluster of cells in upper wall of R atrim - generate waves about 75X/min that spread swiftly over both.
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| Atrioventricular note (AV) | Signal from SA node arrives & a .1s delay occurs before signal given to fire ventricles to contract - Located at interior portion of interatrial septum.
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| Pacemaker potential is due to __. | The special properties of ion channels in sarcolemma - causes influx of calcium that reverses membrane potential.
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| Sequence of excitation of heart. | SA->AV->AV Bundle -> R/L bundle branches -> Purkinje
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| The bulk of bentricular depolarization depends on __. | Purkinje fibers that supply signal to cell-to-cell transmission via gap junctions.
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| Ventricular contraction begins at __ & moves toward? | Heart apex -> atria
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| A defective SA node can have what consequences? | Etopic focus (abnormal pacemaker) where AV node takes over & extrasystole - premature ventricular contraction - PVC's
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| Damage to AV node or __ interferes with ability of ventricles to receive pacing impulses. | heartblock
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| What is the "bundle of His"? | Atrioventricular bundle - electrical connection between the atria & ventricles.
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| The cardiac centers are located __. | in the medulla oblongata
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| P wave on ECG results from? | Movement of depolarization wave from SA node through atria - then atria contract.
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| Blood pressure | The fluid pressure blood exerts against vessel walls. Highest in aorta - measured in mm of mercury (Hg).
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| Systolic pressure | Peak of pressure in aorta while (L) ventricle contracts & pushes blood into the aorta.
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| Diastolic pressure | Lowest blood pressure in aorta when blood is flowing out of it & heart is relaxed.
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| The QRS complex of ECG results from? | Ventricular depolarization & precees ventricular contractions.
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| The T wave of ECG caused by? | Ventricular repolarization
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| During S-T segment of ECG is the __ phase. | plateau
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| Cardiac Output (CO) | Amount of blood pumped out by each ventricle in 1 minute - HR X SV = about 5.25 L /min - little more than 1 gallon
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| Stroke Volume | Volume of blood pumped out by 1 ventricle with each beat.
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| Cardiac reserve for nonathletic people is __ times resting volume, while trained athletes can reach __. | 4-5X, 7
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| SV or stroke volume represents the difference between __ & __. | EDV (end diastolic volume) & ESV (end systolic volume)
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| What is EDV? | End diastolic volvume - the amount of blood that collects in a ventricle during diastole.
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| What is ESV? | The volume of bood remaining in a ventricle after it has contracted - end systolic volume.
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| SV = ? | SV = EDV - ESV
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| Where & what is the point of maximal intenisity (PMI)? | Spot between 5th & 6th ribs where apex contracts the chest wall.
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| External sac (not direct covering) of heart is the __ whose superficial part is the __. | pericardium, fibrous pericardium - dense CT that (1) protects heart, (2) anchors it, (3) prevents overflowing.
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| Deep to fibrous pericardium is __. | Serous pericardium - 2 layer serous membrane
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| 2 layers of serous pericardium is __. | Parietal & visceral (epicardium).
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| Where is the pericardial cavity? | Between parietal & visceral layers - contains serous fluid.
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| Pericarditis is characterized by __. | Pain deep to sternum, creaking sound w/stethoscope.
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| What is cardiac tamponade? | "Heart plug" - excess fluid in pericardial cavity that compresses heart.
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| 3 layers of heart wall. | Epicardium, myocardium, & endocardium
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| Which heart layer is often infiltrated with fat? | Epicardium
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| Which heart layer is composed of cardiac muscle? | Myocardium - the layer that contracts
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| Fibrous skeleton of heart is composed of? | Dense network of CT that reinforces myocardium - collagen & elastin
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| Describe the Frank-Starling law of the heart | The critical factor controlling stroke volume is the preload
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| Preload is? | The degree to which cardiac muscle cells are stretched just before they contract.
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| Resting cardiac cells are normally __ than optimal length. | Shorter
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| The most important factor stretching cardiac muscle is __. | venus return - amount of blood returning to heart.
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| What types of activities increase EDV? Decrease? | Slow heart rate or exercise - blood loss or rapid heart beat
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| Major intrinsic factor influencing SV is? | EDV
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| What intrinsic factor influencing SV is? | EDV (end diastolic volume)
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| What extrinsic factor influences SV? | Increase heart muscle contractility.
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| The contractile strength achieved at a given muscle length. | Contractility
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| An increase in heart cell contractility is due to __. | greater Ca2+ influx into cytoplasm from extracellular fluid & SR.
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| Greater SV means what? | Ejection of more blood from the heart.
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| Contractility is influenced/enhanced by? | Ca2+, glucagon, thyroxine, epinephrine, and the drug digitalis.
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| Negative inotropic agents include? | Acidosis (excessive H+), rising intracellular K+ levels, & calcium channel blockers. All decrease heart conractility.
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| Afterload is? | The pressure that must be overcome for the ventricles to eject blood - back pressure exerted by arterial blood.
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| HR is? | Heart rate
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| What are positive chronotropic factors? | Factors that increase HR
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| The most important extrinsic controls affecting HR. | Autonomic NS
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| SNS releases __ that causes pacemaker cells to fire more rapidly. | NE - Norepinephrine
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| When heart beats faster, there is less tme for __ filling & so a lower __. | Ventricular - EDV
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| Parasympathetic activity has __ effect on cardiac contractility. | little or no
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| Cutting the vagal nerves to heart would do what? | Increase heart rate 25 beats/min due to inherent rate (100 b/m) of pacemaking SA node.
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| Atrial (Bainbridge) reflex | Sympathetic reflex initiated by increased venus return & increased atrial filling - stretching atrial walls increase HR by stim. SA node & atrial stretch receptors.
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| What chemicals influence heart rate? | Hormones, ions - age, gender, exercise, body temp
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| Thyroxine in chronic hyperthyroid individuals __. | May develop a weakened heart due to a slower but more sustained increase in HR.
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| Hypocalcemia __ the heart & hypercalcemia __. | depress - prolong the plateau phase of action potential.
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| What is hyperkalemia & how does it affect the heart. | Excessive K+ may lead to heartblock & cardiac arrest
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| What affect does hypokalemia have on heart? | Lack of K+ heart beats feebly and arrhythmically.
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| Tachycardia results from? | Fast HR (100+ beats/min) - body temp, stress, drugs, or heart disease - promotes fibrillation.
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| Bradycardia results from? Danger is? | Inadequate blood circulation to tissues & a warning of brain edema after head trauma.
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| What is CHF - congestive heart failure? | When CO of heart is so low blood circulation is inadequate to meet tissue needs - weakened myocardium.
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| Dilated cardiomyopathy (DCM) | Ventricles stretch & become flabby & myocardium deteroriates - increased levels of Ca2+ to adapt & heart enlargement.
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| If left side of heart fails it is __. | Pulmonary congestion
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| If right side of heart fails it is __. | peripheral congestion - blood stagnates in body organs - edema
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| The heart is derrived from __. | Mesoderm
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| Foramen ovale is? | Foramen in fetal heart that connects the 2 atria & allows blood entering the right heart to bypass the pulmonary circuit.
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| Ductus arteriosus is? | Another bypass of pulmonary trunk & atria in fetalis
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| Stress of blood flow is greatest where? | Mitral valve
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| 2 classes of BP-lowering drugs. | Beta-blockers & ACE inhibitors.
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