What Do We Need to Know About the Elderly Cardiovascular System

What Do We Need to Know About the Elderly Cardiovascular System? G. Alec Rooke, M.D., Ph.D. Professor of Anesthesiology, University of Washington, and the Veterans Affairs Puget Sound Health Care System rooke@u.washington.edu Why Learn About CV Aging?  Hemodynamic instability is a common annoyance in the OR when treating older patients  BP instability will serve as a framework to review aging CV physiology  Myocardial infarction, heart failure and stroke represent common, major complications of surgery/anesthesia BP Instability is the Hallmark of CV Aging during Anesthesia  MAP = SVR x HR x EDV x EF where:  MAP = mean arterial pressure  SVR = systemic vascular resistance  HR = heart rate  EDV = end-diastolic volume (preload)  EF = ejection fraction (contractility)  Aging makes all variables unstable Systemic Vascular Resistance   Increases with age “Fixed” changes due to connective tissue stiffening (stiffer collagen, less elastin) “Variable” changes from sympathetic nervous system activity  Increased sympathetic tone at rest  Greater swings in sympathetic tone  Greater swings in SVR despite possible decrease in alpha receptor responsiveness  Consequences of Hypertension Late in Systole  Ventricular hypertrophy - leads to delayed relaxation and myocardial stiffening Delayed relaxation impairs early diastolic filling, enhances importance of late filling Late filling depends on atrial pressure and atrial kick to overcome ventricular stiffness   Heart Rate  Diminished heart rate increase in response to stress Reduced maximum heart rate and VO2    Diminished baroreflex control of BP Diminished increase in ejection fraction  dependence on Frank-Starling mechanism to maintain stroke volume  Decreased vagal tone Arrhythmias   Ventricular ectopy is common (benign) Aging damages the conduction system  Loss of SA node cells (90% lost by 80!)  Prolonged P-R interval  Fibrosis of conduction system  Atrial fibrillation and bradycardia are more common in elderly Contractility  Aging does not diminish LV function Rate of contraction slows Strength of contraction maintained  Diminished increase in ejection fraction with beta receptor stimulation dependence on Frank-Starling mechanism (preload) to maintain stroke volume EDV - Cardiac Filling  Depends on venous return and the ability to get blood into the heart Unfortunately, both veins and heart stiffen with age  Decreased Venous Compliance   Veins, like arteries, stiffen with age Stiff veins less able to buffer changes in blood volume (balloon vs pipe)  changes in blood volume produce exaggerated changes in ventricular filling pressure  sympathetic tone affects venous volume and ventricular filling pressure and volume  Changes in filling more dramatically alter cardiac performance and stroke volume Hypertrophy and Aging Stiffen the Heart   Predisposition to diastolic dysfunction may lead to diastolic heart failure Dependence on high atrial pressures is problematic when stiff veins fail to provide a constant preload  End-Diastolic Pressure Dependence on late diastolic filling requires elevated atrial pressure End-Diastolic Volume Anesthetic Management and the Avoidance of Complications     Hypotension Stroke Myocardial Infarction Congestive Heart Failure Should Hypotension be Treated Differently in the Elderly?  MAP = SVR x HR x EDV x EF Target the variable that changes the most Volume loading alone will not restore BP Alpha-agonists support SVR and EDV Inotropes are rarely necessary in the absence of disease    Perioperative Stroke  Risk factors include surgery, age, prior stroke Usually thrombotic or embolic origin  most strokes occur postoperatively  atrial fib or acute MI increase risk  surgery induced hypercoagulability?   Little, if any role, for hypotension  stroke no more likely with hypotension  stroke not more common in border zones  severe hypotension rarely leads to stroke Impaired Ischemic Preconditioning  Aging impairs preconditioning Example of “warm-up angina”  Exercise to point of angina, rest a few minutes, then exert to the point of angina again  Exertion lasts longer time the second time  Increase in duration of exertion begins to decline around age 60, gone by age 75 (J Geront 2000;55A:M124-9 JAGS 1999;47:1114-7)  Congestive Heart Failure   Systolic dysfunction due to disease Diastolic dysfunction alone  Late systolic hypertension → LV stiffening and slowed early relaxation → elevated atrial pressure  Most heart failure in the elderly is solely diastolic failure  Avoid postop CHF by  avoiding myocardial ischemia/infarction  careful fluid administration, judicious furosemide postoperatively Summary  Aging makes all components of blood pressure unstable – control by:  Adequate anesthesia to blunt the highs of surgical stress  Judicious fluid to prevent hypovolemia  Alpha-agonist support  Give fluid in response to hypovolemia  Postop, be prepared to give diuretics  Diastolic heart failure common to elderly  MI and stroke largely thrombotic