Docstoc

ATRIAL FIBRILLATION(9)

Document Sample
ATRIAL FIBRILLATION(9) Powered By Docstoc
					                                                                                    CARDIOLOGY—1
                                                          impact is unknown and no one treatment strategy has
                                                          proven much better than any other at prevention or
    ATRIAL FIBRILLATION                                   treatment.
Common sustained arrhythmic disorder seen in the         Lone Afib: occurring w/out overt evidence of structural
  population at large. prevalence ~ 0.89%, and ~2.2       heart disease by PE, EKG, CXR, and Echo. Does not
  million pt with A fib. Incidence increases w/ (1) Age,  include toxic reactions. Can occur as an isolated event
  (2) presence of structural heart disease, and (3) CHF.  or may be paroxysmal, persistent, or chronic. frequent
Uncommon in patients younger than age 60 years            in younger patients, particularly those with
age-adjusted incidence has  since the 1960s, esp among   paroxysmal Afib.
  men
                                                            Initial Rate Control
Clinical Assessment:                                        Pt with angina or hemodynamic compromise, urgent
Clinical history:                                             cardioversion is usually indicated.
   history of heart failure                                Stable but has a rapid HR, an initial goal is rate control.
   prior transient ischemic attacks                        Pts with rates < 90 bpm may have intrinsic AV node
   prior stroke                                              conduction disease.
   HTN: assessment of stroke risk, and comorbidity         Drug rate control almost invariably requires the use of a
    (mainly the risk of bleeding on anticoagulation)          beta blocker or a calcium channel-blocking agent
   Valvular and structural heart dz: can often be ruled    Specific Rate Control Agents:
    out by Hx, PE, and EKG.
                                                            The most important drugs for rate control are Ca
Lab: Thyroid function studies                                 Channels blockers and Beta-blockers.
Echo and stress testing may be appropriate for
  determining the presence or absence of structural or      Specific Drug Choices:
  ischemic substrates.                                      Stable pt w/out HF —>Diltiazem IV, verapamil,
                                                              metoprolol, propranolol, or atenolol.
Conditions Associated with or Causing Afib                  Potentially unstable and in whom a drug with rapid
Cardiac                                                       onset and offset of action is needed  esmolol.
Valvular heart disease                                      Thyrotoxicosis  B-blockers > response than Ca
Cardiomyopathy (dilated or hypertrophic)                      channel blockers
Coronary artery disease                                     HF  digoxin. Usually inadequate as the sole drug. IV
Hypertension                                                  Amiodarone has also been used for acute rate control.
Surgically repaired congenital heart disease
Primary electrical                                          Often, combo of meds are needed to slow HR.
    Lone atrial fibrillation                                  Whenever rate control cannot be achieved or if a
    Wolff-Parkinson-White syndrome                            patient becomes hemodynamically unstable,
    Reentrant arrhythmia degenerating to atrial               cardioversion is appropriate.
  fibrillation                                              Calcium channel blockers:
                                                            Diltiazem: 0.25 mg/kg IV over 2 min. Repeat 0.35
Noncardiac                                                    mg/kg in 15 min if desired heart rate response not
Thyrotoxicosis                                                achieved. Continuous infusion can be started
Diabetes                                                      immediately after bolus dose at a starting rate of 10
Toxic-Alcohol                                                 mg/h and increased as necessary. Some patients may
Stimulant drugs                                               respond to lower bolus and infusion rates.
Pulmonary disease                                           Verapamil (Isoptin): 5-10 mg IV over 2 min. Repeat
Postoperative                                                 with 10 mg IV after 30 min if desired heart rate
                                                              response not achieved.
Causes of Atrial Fib/Flutter
Poor MISS ATRIAL Fib                                        -blockers:
Pulmonary Embolus                                           Esmolol: 0.5 mg/kg/min IV over 1 min followed by a 4-
                                                              min maintenance infusion of 0.05 mg/kg/ min. A
Mitral Valve Prolapse                                         maintenance drip at 0.05 mg/kg/min can be infused if
Ischemia I Infarction                                         desired heart rate response is achieved. If the heart
Sick sinus syndrome                                           rate remains elevated, a loading dose can be repeated
Sarcoid                                                       and the maintenance dose increased.
                                                            Propranolol: 1-3 mg IV at a rate of 1 mg/min. Repeat
Atherosclerotic CAD                                           after 2 min if desired heart rate response not achieved.
Thyrotoxicosis                                                Drug administration should not be repeated for 4 h.
Rheumatic heart disease                                     Metoprolol: 5 mg IV over 2 min. Repeat every 5 min to
Inflammation (peri-/myocarditis)                              a total dose of 15 mg if desired heart rate response not
Amyloid                                                       achieved.
Lone fibrillation
                                                            Other:
Familial (autosomal dominant)                                Digoxin: 0.25-0.50 mg IV followed by 0.25 mg IV
Types of Atrial Fibrillation                                  every 4-8 h not to exceed 1 mg in 24 h.
                                                             Amiodarone (Cordarone): 5 mg/kg IV over 30 min
Acute: Initial presentation, frequently highly
                                                              followed by 1200 mg over 24 h
  symptomatic. Can result in hemodynamic
  compromise that requires urgent intervention.             Chronic Rate Control Therapy
Paroxysmal: Short, repetitive, often self-limited           Resting HR of 60 to 90 bpm should be maintained.
  episodes of atrial fibrillation lasting from minutes up   Rate control is defined by an average rate of 80 bpm or
  to 7 d.                                                     less over 24 hrs on Holter or rates around 110 bpm
Persistent: Still intermittent episodes of atrial             w/light to moderate exercise, such as a 6-min
  fibrillation but lasting over 2-7 d. Typically requires     treadmill walk.
  intervention for termination.                             Use meds above.
Chronic: Pt always remains in Afib. Restoration of          Data do not support the use of sotalol (Betapace) or
  sinus rhythm not feasible.                                  amiodarone chronically for rate control.
Postoperative: Extremely common after CABG (25-             Digoxin: provides reasonable rate control at rest and is
  30%) and valvular surgery (up to 50%). Prognostic           useful in patients with HF. However, the increases in
2—CARDIOLOGY
  sympathetic tone accompanying exercise typically            either fail to convert with antiarrhythmics or do not
  necessitate addition of either a calcium channel            maintain sinus rhythm after electrical cardioversion,
  blocker or a beta-blocking drug. Care should be taken       despite the use of antiarrhythmics.
  to avoid excessive heart rate blunting in very active
  patients.

Because of underlying heart disease and ventricular
  dysfunction, patients may not tolerate pharmacologic
  efforts at rate control or rate control may be difficult
  to achieve.

Clinical situations in which rate control can be difficult:
1) Decompensated heart failure
2) Severe chronic obstructive lung disease
3) Thyrotoxicosis
4) Conditions with diastolic dysfunction, such as
    hypertrophic cardiomyopathy
Pts with bradycardia-tachycardia syndrome may require
  AVN ablation in conjuction w/permanent pacing early
  in their course to gain control over both ends of their
  heart rate spectrum.
Anticoagulation:
All pt with 1 or > risk factors or echocardiographic risks
     should undergo anticoagulation if possible

Specific risk factors that must be sought are
1) age older than 65 years
2) history of hypertension
3) prior myocardial infarction
4) prior stroke
5) mitral valve stenosis
6) history of prior congestive heart failure
7) Thyrotoxicosis
8) dilated or hypertrophic
9) Cardiomyopathy
10) prior surgical repair of atrial septal defects
11) diabetes.

Echocardiographic risk factors:
1) left ventricular dysfunction
2) left atrial enlargement.

In patients with atrial fibrillation who have clinical risk
  factors for stroke, the risk is around 7.2% per year, in
  comparison with 2.5% per year in those without
  clinical risk factors. If no clinical or
  echocardiographic risk factors are present, the risk of
  stroke is ~ 1% per year.

If warfarin is used  INR range is from 2 to 3.
At an INR < 2, the risk of stroke . Conversely, at an
   INR > 3,  risk of bleeding particularly in the elderly.
Cardioversion:
Acute Cardioversion first episode of atrial fibrillation
      synchronous direct-current shock. IV
     amiodarone, procainamide hydrochloride,
                                   ,i
     propafenone hydrochloride butilide fumarate,
     digoxin, and other agents have been used to
     accomplish acute cardioversion. The earlier they are
     used in the course of A fib, the greater the
     likelihood of successful conversion.
Anticoagulation: anticoagulate prior either electrical or
    chemical cardioversion. INR of 2-3 for > 3 weeks
    before conversion.
TEE used to ID atrial thrombi. This allows earlier
    cardioversion in pts w/A Fib of unknown duration. If
    TEE (-)  cardioversion  anticoagulation
    w/warfarin for several weeks or months.
Electrical Cardioversion: cardioversion alone may not
  improve the clinical status, symptoms, or prognosis of
  the patient with atrial fibrillation. Early recurrences
  after cardioversion are possible, and often a short
  course of antiarrhythmics is given in this event in
  hopes that these changes will normalize as sinus
  rhythm is maintained.
Antiarrhythmics: Also, many patients who have been
  in atrial fibrillation for more than 6 months to 1 year

				
Jun Wang Jun Wang Dr
About Some of Those documents come from internet for research purpose,if you have the copyrights of one of them,tell me by mail vixychina@gmail.com.Thank you!