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74 Cards in this Set
- Front
- Back
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Ventricular escape rhythm
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-Impulse that failed to originate from a pacemaker superior to the ventricles must now develop from within the ventricles themselves.
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Ventricular passive impulses
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-formed when the AV junction fails to produce an impulse.
-Protects the heart from cardiac standstill |
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Ventricular escape beats or rhythms usually occur in response to?
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-an atrial impulse failing to penetrate the AV node, probably because of a high degree of AV block.
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Explain how ventricular rhythms occur?
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-Ventricles having failed to sense an impulse within a prescribed time emit their own impulse at a much slower heart rate.
-Slow rate is due to very slow rate of spontanous diastolic depolarization=20 to 40 bpm |
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Ventricular escape rhythms or idioventricular rhythm originate where?
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-originate anywhere in the ventricles
-close the origin is to common bundle and bundle branches=the narrower the QRS complex is. |
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Explain how the narrow complex results in a wide QRS?
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-narrow complex results from the impulse being able to propagate normally through the ventricles.
-Resulting QRS is wide owing to the impulse originating in the outlying myocardium away from the bundle branches. |
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Ventricular escape beat is how a protective mechanism?
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-protects the heart from extreme slowing or asystole.
-QRS measures 0.12s or greater. |
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Idioventricular rhythms occur when?
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-impulse fails to arrive within a prescribed period of time, it usually has AV dissociation
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Who is at risk?
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-Patients who are scheduled for complete right and left heart catheterization and who have an underlying rhythm of second-degree AV block
-associated bundle branch block are potentially at risk of developing transient or complete heart block owing to the manipulation of catheters within the ventricles. - The resulting ventricular escape rhythm may or may not prove hemodynamically stable and temporary intravenous pacing should be considered as a preventive or interventional measure. |
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Premature Ventricular Contraction (PVC)
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-result of an active impulse formation.
-Mechanisms that produce this irregular beat are reentry, enhanced automaticity, abnormal automaticity and triggered activity. |
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Reentry
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-Results from slow conduction which is often found in ischemic heart disease and conditions that create an electrolyte imbalance.
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Enhanced automaticity
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-is the result of an increase in catecholamine influence. It may well have nothing to do with organic heart disease. Note: sensitivity to caffeine is often an underlying cause of PVC’s.
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PVC's tend to occur more frequently with?
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-age
-latent pacemaker cells and are considered benign unless they are associated with structural or organic heart disease. |
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What are two conditions that give rise to PVCs?
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- Patients suffering from acute MI’s have a greater incidence of Pvc’s during the initial 48 to 72 hours after the infarction. Pvc’s are common in hypertrophy and myocardial scarring.
-Digitalis toxicity is also a common culprit. Patients who are on digitalis should be routinely monitored. If excessive Pvc’s are noted, then digitalis becomes suspect and the physician may subsequently discontinue it. -PVC’s are numerous, then the palpitations may become quite distracting. Palpitations are more noticeable during quiet time rather than when the patient is physically active. -VC generates little stroke volume, and the following sinus beat compensates by ejecting a larger-than-normal stroke volume. This increased volume coupled with the long compensatory pause allows patients to be conscious of an irregularity in their heart rate. |
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When should PVCs be considered malignant?
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-if they result in VTach or Fib associated with myocardial ischemia, syncope or heart failure
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PVC's QRS duration is how long?
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-0.16s or longer suggests an underlying heart disease
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Ectopic focus must first depolarize what?
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-depolarize the left ventricular free wall and subsequently the LV before it is able to penetrate the RBB
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Compensatory Pause
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-delay that follows the PVCs
-Pause demonstrates the inability of the ectopic ventricular impulse to penetrate the AV node retrogradely, so sinus node activity is unaffected. |
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PVC with full compensatory pause?
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-PVC in the ECG is wideneed and premature.
-Pause follows the PVC reflects the inability of the next sinus impulse to propagate through the ventricles. -Next sinus beat occurs as expected. -Interval from the preceding sinus beat and following sinus beat will usually be twice that of the underlying sinus interval (RR interval). |
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What leads to a PVC with a long compensatory pause?
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-PVC that is able to conduct retrogradely to the AV node finds the node refractory due to the next sinus beat having already arrived.
-Thus the sinus beat is prevented from conducting through as well. |
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Torsades De Pointes (Twisting the Points)
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-Another form of VT
-Manifested in conditions that prolong the QT interval |
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What prolongs the QT interval?
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-quinidine
-amiodarone therapy -congenital QT prolongation syndrome -electrolyte disturbances -Coronary artery disease |
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How does the arrhythmia result from premature beat?
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-occurs during the vulnerable period of ventricular repolarization (T wave) and initiates a VTACH or R on T phenomenon.
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What gives the ECG a sinusodial type of pattern?
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-Amplitude and polarity of the QRS are constantly changing
-Arrhythmia may be as slow as 100 bpm or fast as 300 bpm |
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What is the key to treating the arrhythmia?
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-Alleviate the underlying cause
-If the arrhythmia is drug related, the drug must be stopped -Patients who undergo cardiac catheterization and are on quinidine therapy and have prolonged QT interval should be closely monitored. |
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How is VFIB or VFlutter distinguishable?
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-PQRST absent
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Ventricular Flutter
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-Wavefroms appear to be regular
-ECG looks the same whether read right side up or upside down -Large flutter waves tend to indicate a healthier heart -Smaller flutter waves means fibrillation |
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Ventricular Fibrillation
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-Rate 200 to 300 bpm
-Occurs when the heart is no longer pumping and its quivering. -CO drops to Zero=pxn hemodynamically collapses -Death in less than 4 mins -Can be reversed with defib -irregular waveform |
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What are two forms of DC Shock?
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-Cardioversion
-Defibrillator |
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Cardioversion
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-synchronized discharge of electricity
-Convert certain supraventricular and ventricular arrhythmias to NSR |
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What is imperative or important with synchronization of cardioversion?
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-synchronization with the QRS is imperative in preventing a DC current from being discharged during the vulnerable period of ventricular repolarization.
-if this happens=higher chances of VFIB |
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Cardioversion is used for what arrhythmias?
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- atrial fibrillation or flutter, supraventricular tachycardias resistant to vagal maneuvers or to drug therapy and ventricular tachycardia that is refractory to drug therapy.
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Defibrillator
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-Non synchronized
-It is used most often in ventricular fibrillation when there is no identifiable QRS and T wave morphology. |
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Patients with inital hours of an acute MI may be treated with?
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-lidocaine
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PVCs that occur in the cardiac cath lab as a result of catheter manipulation are generally not?
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-treated; they are subsided when the catheter is removed
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PVC's that occur during pacemaker lead implantation alert the surgeon to?
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-investigate other options for lead placements
-Sometimes the placement options are limited and the patient may have to be prescribed meds to help reduce the PVCs |
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What defines VTACH?
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- 3 or more PVCS occur in succession
-Rate is exceeding 100 bpm -This is usually a reentry mechanism |
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The setting for reentry is most commonly found in?
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-MIs and coronary artery disease
-This pathologies provide the damaged myocardium needed for slowed conduction and the development of reentry loops. |
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How do cardiomyopathies initiate VT?
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-alter the septal conduction thereby altering the temporal relationship between the two bundle branches=VT
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What poisoning alters the action potential in His-Purkinje system to promote VT?
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-Digitalis toxicity sufficiently alters the action potential in the His-Purkinje system to promote the triggered VT.
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Arrhythmogenesis of VT can be explained by revisting what?
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-the cardiac cell and looking at what happens during acute ischemia and MI. The changes in the intracellular and extracellular space are the result of anoxia and anaerobic metabolism.
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Brugada Syndrome
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affects the early repolarization phase of the action potential (phases 1-2) can trigger VT and/or VF by automaticity. The disease is most prevalent in Asia and responds well with ICD therapy if diagnosed in time.
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How does the cell becomes more acidotic and cellular uncoupling results?
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-Initial occlusion of the coronary artery causes a loss of potassium into the extracellular space
- Then an extracellular increase in catecholamine levels follows -On the cell’s death, the extracellular potassium again rises, owing to a total loss of membrane integrity. -Concentrations of intracellular calcium rise during this time and the cell becomes more acidotic and cellular uncoupling results. |
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Afterdepolarizations
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-increase in calcium is also responsible for a transient inward current which decreases the membrane potential and leads to afterdepolarizations.
-these depolarizations that can reach threshold potential and trigger the action potentials that produce a spontaneous premature beat (a PVC). Circulating catecholamines increase the likelihood of triggered activity in the ischemic zone. |
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What prevents the Na channels from opening?
(First step Reentry mechanism to develop) |
-Increased potassium in the extracellular space has led to a less negative resting voltage potential of neighboring cells thereby preventing NA channels from opening
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What diminishes the conduction velocity and increase automaticity? How is the reentry mechanisms to develop 2nd Step
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-Action potential in ventricles is primarily Na-dependent, ischemic zones will provide the necessary substrate for diminished conduction velocity and increased automaticity.
-Stage is now set for a reentry mechanism to develop. |
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Multifocal or polymorphic VT
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-arrhythmia that demonstrates multiple ectopic foci and is precursor to VFlutter or Vfib
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Fascicular ventricular tachycardias
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-originate from the septal region and often produce a narrow QRS complex.
-VTACH is provoked, it sustains itself or self-terminates. |
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Nonsustained VT and sustained terminates when?
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-self-terminates 30 seconds or less
-sustained VT persists for more than 30 seconds and often leads to hemodynamic compromise. |
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VTACH is one of the leading causes of?
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-AV dissociation
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Atrial are controlled by?
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-supraventricular pacemaker while the ventricles are controlled by ventricular ectopic focus
-Two pacemaker sites beat independently for each other, a beat-to-beat change in BP results from the constantly changing SV in aorta |
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Wide-complex QRS supraventricular tachycardias
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-appear just like VT
-Result of aberrant conduction not of ventricular ectopic activity -Accomplished by evaluating the QRS morphology in leads V1 and V6. |
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How do you treat a person with SVT and patient that is unstable?
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-immediate cardioversion is warranted
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When is drug Procainamide (Pronestyl) used?
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-used to prolong the refractory period of the ventricles and accessory pathways.
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What techniques is used to treat SVT
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-vagal stimulation
-coughing -CSM -Valsalva Maneuver |
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Verapamil
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-given to block conduction in the AV node
-Inadvertently given to treat VT, it can lead to serious hemodynamic compromise and cardioversion may prove unsuccessful |
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What are some signs and symptoms of VT?
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-difficulting in breathing
-loss of conciousness -eyes rolled back -IMMEDIATE ACTION IN FORM OF ELECTROCARDIOVERSION |
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patient is in a stable VT or SVT and shows no sign of hemodynamic compromise, the physician may opt for the following:
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Overdrive pacing (successful in some VTs)
• Appropriate pharmacological intervention VT: lidocaine, procainamide, or bretylium SVT: procainamide, adenosine, or verapamil • Vagal maneuvers (in the case of SVT) • DC shock (if none of the previous methods is successful) |
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List some guidelines for Proper use of Cardiac Defibrillator
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-defib is quality controlled regulary and that the electrical integrity is verified
-Make appropriate paddles available (anterior posterior or two anteriors) -Administer transient amnesia to patient (valium or morphine) -When you use posterior paddles, apply liberal amount of paste (prevent skin burns) -Ensure the pxns skin are not touching other metal or part of the bed at time of DC shock -Restrain the pxns hands and arms to avoid injury -Defib is charged to the energy level requested by physician |
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What complications arise when applying defib?
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-technical errors that occur with failure to synchronize the electrical discharge, an ECG artifact discharging during the T wave and use of excessive energy.
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Electromechanical dissociation (EMD)
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-replaced with PEA (pulse-less electrical activity).
-terms reference the organized electrical activity on the ECG but failure of effective perfusion (no pulse or BP). -Patients with EMD/PEA have primary Myocardial failure |
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Causes of EMD/PEA that are most treatable are?
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Hypovolemia due to severe bleeding
Pericardial tamponade Pneumothorax |
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In Acute MI, sudden EMD/PEA is a sign of?
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-mycoardial rupture
-In this case, pericardiocentesis and surgical repair rarely result in survival |
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Whats another condition that can cause EMD/PEA is?
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-post cardiopulmonary resuscitation and no pulse or evidence of perfusion is seen
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Ventricular standstill (cardiac arrest) is characterized by?
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-absence of any ventricular activity in the ECG
-There is no cardiac pacemaker activity or contractions |
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Ventricular standstill may occur when?
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-After DC shock of other tachy arrhythmias
-As the end stage of a dying heart following VT, VF, and Ventricular Flutter -Prolonged standstill will almost always produce Adams-Stokes syndrome -Cardiac arrest, it is important that cardiac activity be restored immediately by CPR or artificial pacing or both. |
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Agonal rhythms
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-prevalent in dying heart
-Complexes are bizarre, wide, and usually irregular and are recorded at extremely slow rates. -HR is less than 20 bpm and the complexes hold no rule in conforming to a true LBBB or nodal beat. |
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Multifocal or polymorphic in appearance?
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-PVCs that develop from two or more ectopic foci give rise to different morphologies
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Polymorphic and coupled PVC
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-from two or more ectopic foci give rise to different morphologies
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Bigeminy, tigeminy, quadrigeminy
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bigeminy: PVC every other beat
Trigeminy: Occuring regularly every third beat Quadrigeminy: occur every 4th beat |
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When 3 or more PVCs occur together, it is called?
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-Ventricular tachycardia
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Manipulating catheters in the right and left ventricles often produces what?
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-isolated PVCs or short runs of three to five coupled PVCs.
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What are pharmalogical interventions of VT?
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-lidocaine
-procainamide -bretylium |
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Pharmalogical intervention for SVT?
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-procainamide
-Adenosine -verapamil |
