|
|
| Line 11: |
Line 11: |
|
| |
|
| ==Differential Diagnosis of Wide Complex Tachycardia== | | ==Differential Diagnosis of Wide Complex Tachycardia== |
| ===EKG Findings Suggestive of VT===
| | There are several EKG criteria that may help differentiate [[ventricular tachycardia]] ([[VT]]) from [[supraventricular tachycardia]] ([[SVT]]) with aberrancy in the patient with a wide complex tachycardia. The diagnosis of [[VT]] is more likely if |
| ====History of Ischemic Heart Disease====
| | *The [[electrical axis]] is -90 to -180 degrees (a “northwest” or “superior” axis) |
| A history of [[ischemic heart disease]] or structural heart disease suggests VT. Wide complex tachycardia will be due to [[VT]] in 80% of cases if there is a history of [[myocardial infarction]] ([[MI]]). Only 7% of patients with SVT will have had a prior myocardial infarction (MI). Wide complex tachycardia will be due to [[VT]] in 98% of cases if there's a history of structural heart disease.
| | *The [[QRS]] is > 140 msec |
| | *There is [[AV dissociation]] |
| | *There are positive or negative [[QRS]] complexes in all the precordial leads |
| | *The morphology of the [[QRS]] complexes resembles that of a previous [[premature ventricular contraction]] ([[PVC]]). |
|
| |
|
| ====The Presence of AV Dissociation====
| | For more detailed information regarding how to differentiate VT from SVT click here. |
| Although AV dissociation is highly suggestive of VT, it may also be seen in [[junctional tachycardia]]s with retrograde block.
| |
| | |
| Example: Shown below is a wide complex tachycardia. [[AV dissociation]] is present as shown by the varying morphology highlighted by the red arrows. [[LBBB]] configuration. Absence of RS in the chest leads. The diagnosis is [[VT]].
| |
| [[Image:wide_qrs_tachy_AAM3.png|center|700px]]
| |
| | |
| Example: Shown below is a wide complex tachycardia. [[AV dissociation]] is present as shown by the varying morphology highlighted by the red arrows. LBBB configuration. Absence of RS in the chest leads. The diagnosis is [[VT]].
| |
| [[Image:wide_qrs_tachy_AAM4.png|center|700px]]
| |
| | |
| ----
| |
| | |
| ====Duration of the QRS Complex====
| |
| * A wide complex tachycardia with a [[RBBB]] morphology and a QRS > 0.14, or a [[LBBB]] morphology with a QRS > 0.16 suggests [[VT]].
| |
| | |
| ====Morphology of the QRS Complexes====
| |
| * The finding of a positive or negative QRS complex in all precordial leads is in favor of [[ventricular tachycardia]].
| |
| * A monophasic or biphasic RBBB QRS complex in V1. But none of their patients with SVT had a preexisting RBBB. Therefore, this finding is of limited importance (A Wellens criterion).
| |
| * 80 to 85% of aberrant beats have a RBBB pattern, but ectopic beats that arise from the LV have a similar morphology.
| |
| * LBBB with a rightward axis
| |
| * LBBB with the following QRS morphology:
| |
| :* R wave in V1 or V2 > 0.03 second
| |
| :* Any Q wave in V6
| |
| :* Onset of the QRS to nadir of the S wave in V1 > 0.06 seconds
| |
| :* Notching of the S wave in V1 or V2
| |
| | |
| {| class="wikitable" width="500px"
| |
| ! colspan="3" | Morphological criteria
| |
| |-
| |
| !colspan="3" |[[LBBB]] pattern
| |
| |-
| |
| | Initial R more than 40 ms? ||Yes ≥ VT || [[Image:Rhythm_RSratio.png|thumb|100px]]
| |
| |-
| |
| | Slurred or notched downwards leg of S wave in leads V1 or V2? || Yes ≥ [[VT]] ||
| |
| |-
| |
| | Beginning of Q to nadir QS > 60 ms in V1 or V2? || Yes ≥ [[VT]] || LR > 50:1
| |
| |-
| |
| | Q or QS in V6? || Yes ≥ [[VT]] || LR > 50:1
| |
| |-
| |
| | colspan="3" |[[Image:Rhythm_LBTBmorph_nl.png|thumb|300px]]
| |
| |-
| |
| ! colspan="3" |[[RBBB]] pattern
| |
| |-
| |
| | Monofasic R or qR in V1? ||Yes ≥ [[VT]] ||
| |
| |-
| |
| | R taller than R' (rabbit-ear sign)?||Yes ≥ [[VT]] || LR > 50:1
| |
| |-
| |
| | rS in V6? || Yes ≥ VT || LR > 50:1
| |
| |-
| |
| |}
| |
| {{clr}}
| |
| | |
| ----
| |
| | |
| ====Morphology of Premature Beats During Sinus Rhythm====
| |
| * If [[premature ventricular contractions]] ([[PVCs]]) are present on a prior tracing, and if the morphology of the wide complex tachycardia is the same, then it is likely to be ventricular tachycardia.
| |
| * Previous EKG may show a preexisting [[intraventricular conduction delay]] ([[IVCD]]) which would favor SVT with abberancy.
| |
| * If there are [[premature atrial contractions]] ([[PAC]])s with aberrant conduction, then the origin of the wide complex tachycardia may be supraventricular.
| |
| | |
| :Example: Shown below is a wide complex tachycardia. There is no AV dissociation. A [[RBBB]] morphology is present. The wide complex tachycardia resembles [[sinus rhythm]] from the same patient. The diagnosis in this patient is SVT with [[RBBB]]:
| |
| [[Image:wide_qrs_tachy_AAM1.jpg|center|700px]]
| |
| | |
| :Shown below is the ECG from the same patient as above in sinus rhythm. The QRS complex is very similiar to that during the wide complex tachycardia:
| |
| [[Image:wide_qrs_tachy_AAM2.jpg|center|700px]]
| |
| ----
| |
| | |
| ====The QRS Axis====
| |
| *A "northwest axis" with a [[QRS axis]] in the RUQ between -90 and +180 degrees favors [[ventricular tachycardia]].
| |
| | |
| :The image below illustrates the "Northwest axis"also known as "Extreme Right Axis" or "No Man's Land":
| |
| [[File:QRS axis.PNG|center|600px]]
| |
| | |
| ====Capture Beats====
| |
| * Rare, but one of the strongest pieces of evidence in favor of VT.
| |
| * SVT with aberrancy rarely follows a beat with a short cycle length.
| |
| | |
| ====Fusion Beats====
| |
| :[[Fusion beats]] are rare, but strongly suggests VT.
| |
| [[File:VT with fusion beats.jpg|center|800px]]
| |
| | |
| ----
| |
| | |
| ====Vagal Manuevers====
| |
| * VT is generally not affected by vagal stimulation.
| |
| * May terminate reentrant arrhythmias
| |
| | |
| ====Atrial Pacing====
| |
| * A pacing wire is placed in the RA and the atrium is stimulated at a rate faster than the tachycardia.
| |
| * If ventricular capture occurs and the QRS is normal in duration, then one can exclude the possibility of aberrant conduction.
| |
| | |
| ====Onset of the Tachycardia====
| |
| * Diagnosis of SVT made if the episode is initiated by a premature P wave.
| |
| * If the paroxysm begins with a QRS then the tachycardia may be either ventricular or junctional in origin.
| |
| * If the first QRS of the tachycardia is preceded by a sinus p wave with a PR interval shorter than that of the conducted sinus beats, the tachycardia is ventricular.
| |
| | |
| ====His Bundle Recording====
| |
| * In SVT, each QRS is preceded by a His bundle potential.
| |
| * In VT there is no preceding His deflection.
| |
| * The retrograde His deflection is usually obscured by the much larger QRS complex.
| |
| | |
| ====Regularity of the Rhythm====
| |
| =====Regular=====
| |
| * VT (slight irregularity of RR)
| |
| * SVT with aberrancy: Sinus, atrial tachycardia (AT), or flutter
| |
| * Antidromic atrioventricular reentrant tachycardia (AVRT)
| |
| | |
| =====Irregular=====
| |
| * The first 50 beats of VT can be irregular
| |
| * SVT with aberrancy: [[Atrial fibrillation]], multifocal atrial tachycardia (MAT)
| |
| * [[Atrial fibrillation]] with bypass tract usch as [[WPW]] is a dangerous cause of a very rapid irregular rhythm as the atrial rate is conducted rapidly over the bypass tract. Shown below is the tracing of a patient with [[atrial fibrillation]] conducting down the bypass tract in [[WPW]]. Note that the rate is extremely rapid, and the rhythm is irregularly irregular. It is critical that this rhythm be recognized to avoid the administration of agents that would further accelerate conduction down the accessory pathway in this patient with [[WPW]] which could cause degeneration into [[ventricular fibrillation]]. The best treatment for this patient is [[Pronestyl]] 15 mg/kg load over 30 minutes then 2-6 mg/min gtt or DC [[cardioversion]]:
| |
| | |
| [[File:Wpw with afib.PNG|center|500px]]
| |
| ----
| |
| * The mechanism of SVT with aberrancy is usually concealed retrograde conduction. The ventricular beat penetrates the right branch (RB) or left branch (LB). When the next supraventricular activation front occurs that bundle is refractory and if conduction can occur, it will proceed down the other bundle. Since the RB has a longer refractory period than the LB, a right bundle branch block (RBBB) morphology is more common.
| |
| * Other mechanisms of “rate related aberrancy” are preexisting bundle branch block (BBB), physiologic (phase 3) aberration and use dependent aberration secondary to medication. In physiologic aberration, the stimulus comes to the His-Purkinje system before it has fully recovered from the previous stimulus. The ensuing activation is either blocked or conducts slowly. Again, the RB is the one more at risk. Most commonly seen at the onset of paroxysmal supraventricular tachycardia (PSVT), but can become sustained.
| |
| * In use-dependent aberration, a patient on and anti-arrhythmic (especially class Ic agents) will have a progressive decrement in ventricular conduction rate the more it is stimulated. During faster heart rates, less time is available for the drug to dissociate from the receptor and an increased number of receptors are blocked.
| |
| ----
| |
| | |
| ===Sophisticated Electrophysiologic Criteria===
| |
| Several [[ECG]] criteria and algorithms have been used to differentiate [[VT]] and [[SVT]], the common one of which is Brugada algorithm. Below is a list of all algorithms:
| |
| * Brugada algorithm: sensitivity 89%, specificity 59.2%<ref name="pmid2022022">{{cite journal| author=Brugada P, Brugada J, Mont L, Smeets J, Andries EW| title=A new approach to the differential diagnosis of a regular tachycardia with a wide QRS complex. | journal=Circulation | year= 1991 | volume= 83 | issue= 5 | pages= 1649-59 | pmid=2022022 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=2022022 }} </ref>
| |
| | |
| * The lead II R-wave-peak-time: sensitivity 60%, specificity 82.7%<ref name="pmid20215043">{{cite journal| author=Pava LF, Perafán P, Badiel M, Arango JJ, Mont L, Morillo CA et al.| title=R-wave peak time at DII: a new criterion for differentiating between wide complex QRS tachycardias. | journal=Heart Rhythm | year= 2010 | volume= 7 | issue= 7 | pages= 922-6 | pmid=20215043 | doi=10.1016/j.hrthm.2010.03.001 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=20215043 }} </ref>
| |
| | |
| * The aVR algorithm: sensitivity 87.1%, specificity 48%<ref name="pmid17272358">{{cite journal| author=Vereckei A, Duray G, Szénási G, Altemose GT, Miller JM| title=Application of a new algorithm in the differential diagnosis of wide QRS complex tachycardia. | journal=Eur Heart J | year= 2007 | volume= 28 | issue= 5 | pages= 589-600 | pmid=17272358 | doi=10.1093/eurheartj/ehl473 | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=17272358 }} </ref>
| |
| | |
| * The Bayesian algorithm: sensitivity 89%, specificity 52%<ref name="pmid11060873">{{cite journal| author=Lau EW, Pathamanathan RK, Ng GA, Cooper J, Skehan JD, Griffith MJ| title=The Bayesian approach improves the electrocardiographic diagnosis of broad complex tachycardia. | journal=Pacing Clin Electrophysiol | year= 2000 | volume= 23 | issue= 10 Pt 1 | pages= 1519-26 | pmid=11060873 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=11060873 }} </ref>
| |
| | |
| * The Griffith algorithm: sensitivity 94.2%, specificity 39.8%<ref name="pmid7905552">{{cite journal| author=Griffith MJ, Garratt CJ, Mounsey P, Camm AJ| title=Ventricular tachycardia as default diagnosis in broad complex tachycardia. | journal=Lancet | year= 1994 | volume= 343 | issue= 8894 | pages= 386-8 | pmid=7905552 | doi= | pmc= | url=http://www.ncbi.nlm.nih.gov/entrez/eutils/elink.fcgi?dbfrom=pubmed&tool=sumsearch.org/cite&retmode=ref&cmd=prlinks&id=7905552 }} </ref>
| |
| ====The R Wave Peak Time====
| |
| In 2010 Joseph Brugada et al. published a new criterion to differentiate VT from SVT in wide complex tachycardias: the R wave peak time (RWPT) in Lead II.<ref name="pmid20215043">{{cite journal |author=Pava LF, Perafán P, Badiel M, Arango JJ, Mont L, Morillo CA, Brugada J |title=R-wave peak time at DII: a new criterion for differentiating between wide complex QRS tachycardias |journal=[[Heart Rhythm : the Official Journal of the Heart Rhythm Society]] |volume=7 |issue=7 |pages=922–6 |year=2010 |month=July |pmid=20215043 |doi=10.1016/j.hrthm.2010.03.001 |url=http://linkinghub.elsevier.com/retrieve/pii/S1547-5271(10)00216-X |issn= |accessdate=2012-10-13}}</ref> To aplly the criteria, the duration of onset of the QRS to the first change in polarity (either nadir Q or peak R) is measured in lead II as shown below. If the RWPT is ≥ 50ms the likelihood of a VT very high (positive likelihood ratio 34.8). This criterion was successful in their own population of 163 selected patients and is awaiting prospective testing in a larger trial.
| |
| | |
| Example: As shown below, an R-wave to Peak Time (RWPT) of ≥ 50ms in lead II strongly suggests VT:
| |
| [[File:RWPT.png|center|500px]]
| |
| | |
| ====Brugada Criteria====
| |
| {{familytree/start}}
| |
| {{familytree | | | | | | A01 |-|-|-|-|-| A02 |A01=Absence of an RS complex<br> in all precordial leads?|A02='''Yes?'''<br><br>'''VT''' (SN=0.21 SP=1.0)}}
| |
| {{familytree | | | | | | |!| | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | B01 | | | | |B01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | }}
| |
| {{familytree | | | | | | C01 |-|-|-|-|-| C02 |C01=R to S interval>100 ms in <br>one precordial lead?|C02='''Yes?'''<br><br>'''VT''' (SN=0.21 SP=1.0)}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | D01 | | | | | | | | | | | | |D01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | E01 |-|-|-|-|-| E02 | | |E01=AV dissociation?|E02='''Yes?'''<br><br>'''VT''' (SN=0.82 SP=0.98)}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | F01 | | | | | | | | | | | | |F01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | G01 |-|-|-|-|-| G02 | | |G01=Morphology criteria for VT present<br> both in precordial leads V1, V2 and V6?|G02='''Yes?'''<br><br>'''VT''' (SN=0.987 SP=0.965)}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | H01 | | | | | | | | | | | | |H01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | I01 | | | | | | | | | | | | |I01='''SVT''' (SN=0.965 SP=0.987)}}
| |
| {{familytree/end}}
| |
| | |
| ====Vereckei Criteria====
| |
| * An algorithm has been proposed by Vereckei and colleagues, wherein in addition to do the traditional criteria, the voltage change on the EKG is used as a final discriminatory criteria.
| |
| * In this method, the voltage change during the initial 40 ms (V<sub>i</sub>) and the terminal 40 ms (V<sub>t</sub>) of the same QRS complex is used to estimate the (V<sub>i</sub>) and terminal (V<sub>t</sub>) ventricular activation velocity ratio (V<sub>i</sub>/V<sub>t</sub>).
| |
| * A V<sub>i</sub>/V<sub>t</sub> > 1 suggests SVT and a V<sub>i</sub>/V<sub>t</sub> ≤ 1 suggests VT.<ref name="pmid17272358">{{cite journal |author=Vereckei A, Duray G, Szénási G, Altemose GT, Miller JM |title=Application of a new algorithm in the differential diagnosis of wide QRS complex tachycardia |journal=[[European Heart Journal]] |volume=28 |issue=5 |pages=589–600 |year=2007 |month=March |pmid=17272358 |doi=10.1093/eurheartj/ehl473 |url=http://eurheartj.oxfordjournals.org/cgi/pmidlookup?view=long&pmid=17272358 |issn= |accessdate=2012-10-13}}</ref>
| |
| | |
| | |
| {{familytree/start}}
| |
| {{familytree | | | | | | A01 |-|-|-|-|-| A02 |A01=AV dissociation present?|A02='''Yes?'''<br><br>'''VT'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | B01 | | | | |B01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | }}
| |
| {{familytree | | | | | | C01 |-|-|-|-|-| C02 |C01=Initial R wave in aVR present?|C02='''Yes?'''<br><br>'''VT'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | D01 | | | | | | | | | | | | |D01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | E01 |-|-|-|-|-| E02 | | |E01=QRS morphology unlike BBB or FB|E02='''Yes?'''<br><br>'''VT'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | F01 | | | | | | | | | | | | |F01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | G01 |-|-|-|-|-| G02 | | |G01=V<sub>i</sub>/V<sub>t</sub>≤1?|G02='''Yes?'''<br><br>'''VT'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree |border=0| | | | | | H01 | | | | | | | | | | | | |H01='''No?'''}}
| |
| {{familytree | | | | | | |!| | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | I01 | | | | | | | | | | | | |I01='''SVT'''}}
| |
| {{familytree/end}}
| |
| | |
| =====Calculation of V<sub>i</sub>/V<sub>t</sub>=====
| |
| Shown below is an image demonstrating the method used to calculate Vi/Vt. In this tracing, Vi/Vt is < 1 is suggestive of [[ventricular tachycardia]] according to Vereckei criteria.
| |
| | |
| [[File:Vivt.png|350px]]
| |
| ----
| |
| | |
| ===Putting it all together: The ACC Algorithm===
| |
| {{familytree/start}}
| |
| {{familytree | | | | | | | | | | | | | | | | | A01 | | | | | |A01='''Wide QRS complex tachycardia'''<br>(QRS duration greater than 120 ms)}}
| |
| {{familytree | | | | | | | | | | | | | | | | | |!| | | | | | | | }}
| |
| {{familytree | | | | | | | | | | | | | | | | | B01 | | | | | |B01=Regular or irregular?}}
| |
| {{familytree | | | | | | | | | | |,|-|-|-|-|-|-|^|-|-|-|-|-|-|.| }}
| |
| {{familytree | | | | | | | | | | C01 | | | | | | | | | | | | C02 |C01=Regular|C02=Irregular}}
| |
| {{familytree | | | | | | | | | | |!| | | | | | | | | | | | | |!| }}
| |
| {{familytree | | | | | | | | | | |)|-| D01 | | | | | | | | | D02 |D01=Is QRS identical to that during SR?<br>If yes, consider:<br> '''- SVT and BBB<br> - Antidromic AVRT'''|D02='''Atrial fibrillation<br>Atrial flutter / AT with variable<br> conduction and:<br>a) BBB or<br>b) Antegrade conduction via AP'''}}
| |
| {{familytree | | | | | | | E01 |-|(| | | | | | | | | | | | | |E01=Vagal maneuvers or<br>adenosine}}
| |
| {{familytree | | | | | | | | | | |)|-| E02 | | | | | | | | | |E02=Previous myocardial infarction or structural heart disease? If yes, '''VT''' is likely.}}
| |
| {{familytree | | | | | | | | | | |!| | | | | | | | | | | | | | | }}
| |
| {{familytree | | | | | | | | | | F01 | | | | | | | | | | | | | |F01=1 to 1 AV relationship?}}
| |
| {{familytree | | | | | |,|-|-|-|-|^|-|-|-|-|-|-|-|-|.| | | | | | }}
| |
| {{familytree | | | | | G01 | | | | | | | | | | | | G02 | | | | | G01= Yes or unknown| G02= No}}
| |
| {{familytree | | | | | |!| | | | | | | | | | | | | |!| | | | | | }}
| |
| {{familytree | | | | | |!| | | | | | | | | | | |,|-|^|-|.| | | | }}
| |
| {{familytree | | | | | |!| | | | | | | | | | | H01 | | H02 | | |H01= V rate faster than A rate|H02=A rate faster than V rate}}
| |
| {{familytree | | | | | |!| | | | | | | | | | | |!| | | |!| | | | }}
| |
| {{familytree | | | | | I01 | | | | | | | | | | H03 | | H04 | | | I01=QRS morphology in precordial leads| H03='''VT'''|H04='''Atrial tachycardia'''<br>'''Atrial flutter'''}}
| |
| {{familytree | |,|-|-|-|+|-|-|-|v|-|-|-|.| | | | | | | | | | | | }}
| |
| {{familytree | |!| | | |!| | | |!| | | |!| | | | | | | | | | | | }}
| |
| {{familytree | J01 | | J02 | | J03 | | J04 | | | | | | | | | | | J01= Typical RBBB <br> or LBBB| J02=Precordial leads:<br>- Concordant<br>- No R/S pattern<br>- Onset of R to nadir longer than 100ms<br>| J03=RBBB pattern:<br>- qR, Rs or Rr' in V1<br>- Frontal plane axis range<br>from +90 degrees to -90 degrees<br>| J04=LBBB pattern:<br> - R in V1 longer than 30 ms<br>- R to nadir of S in V1 greater than 60 ms<br>- qR or qS in V6}}
| |
| {{familytree | |!| | | |!| | | |!| | | |!| | | | | | | | | | | | }}
| |
| {{familytree | K01 | | K02 | | K03 | | K04 | | | | | | | | | | |K01= '''SVT'''|K02='''VT'''|K03='''VT'''|K04='''VT'''}}
| |
| {{familytree/end}}
| |
| | |
| | |
| ''The above algorithm is adapted from the American College of Cardiology.''
| |
|
| |
|
| ==References== | | ==References== |