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BSc module 2 > CRT and pacing > Flashcards

CRT and pacing Flashcards

1
Q

What is CRT

A

pacemaker therapy to improve symptoms and mortality of HF

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2
Q

What percentage of HF patients have impaired systolic function and how many of these have severely impaired LVEF (<50%)

A

50%

1/4 of these

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3
Q

Who benefits from CRT

A

HFrEF
have severely impaired LVEF (<50%)
benefit the post

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4
Q

CRT in HFpeF?

A

No real evidence for HFpEF

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5
Q

Why CRT?

A

Pt with cardiac dyssynchrony appear to do worse

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6
Q

Medical therapy for HF

A

ACEi
Beta blockers
Spironalactone

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7
Q

Terminology:

CRT-P

A

Purely ability of a pacemaker to make walls contract at the same time.
Without defibrillator

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8
Q

Terminology

CRT-D

A

CRT with defibrillator function

- Replace RV lead with defibrillator

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9
Q

Leads of CRT

A

Atrial lead, RV lead (defibrillator or normal pacemaker lead), LV lead (important lead

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10
Q

Important lead in CRT

A

LV lead

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11
Q

Path of LV lead

A

across the heart, through the coronary sinus to lateral surface of the LV
- Stimulation of left ventricle via a vein, whole wire is in contact with the heart

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12
Q

Layer of heart that the CRT leads are attached to

A

LV - Epicardium

Atrial and RV - Endocardium

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13
Q

Another current name for CRT

A

Biventricular pacing

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14
Q

What is dual chamber pacing?

A

Not CRT
- Refers to atrium and RV
NOT CRT

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15
Q

What is cardiac dyssynchrony?

A

Uncoordinated activity of the heart

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16
Q

Normal activation of heart in layers

A

Endocardial to epicardial

17
Q

Ways to think of dyssynchrony

A
  1. Electrical

2. Mechanical

18
Q

What is mechanical dyssynchrony?

A

Can occur without significant electrical dyssynchrony
Normal QRS measures but echo measures of dyssynchrony
Not entirely understood:
- Latency in diseased hearts? leading to a delay between
the two (even through activation has occurred it takes
time for contraction to follow
- Or conduction disease is not visible to use in the
surface ECG? Electrical dyssynchrony is there we just cannot see it

19
Q

What is electrical dyssynchrony?

A

Conduction problem that is resulting in the walls not contracting at the same time. Contribute to and/or cause mechanical dyssynchrony

Long PR: (AVB)
Long QRS: (LBBB, RBBB, IVCD)

20
Q

Significants of LV lead in LBBB

A

Allows activation of lateral LV wall earlier than would have occurred in LBBB

21
Q

Impact of CRT on mechanical/electrical dyssynchrony

A

removes mechanical dyssynchrony as it ensures everything contracts as and when it should
Electrical dyssynchrony is also shown to disappear

22
Q

Impact of CRT on CO?

Does it really work

A

Pulmonary capillary wedge pressure reduced (heart lesss overloaded)
CO has significantly increased, improved contraction.
BUT same is seen for many inotropes (dopamine, dobutamine, milrinone).
Long term, survival probability is reduced with inotropic agents

23
Q

CRT vs Inotropes survival and hospital admission

A

CRT much better - CARE-HF

24
Q

Meta-analyses of >20 RCTs

A

Odds ratio favouring CRT over medical therapy

- Decreased mortality by almost 30%

25
Q

Optimization of CRT

A
  • Epi to endo is non-physiological
  • RV apical pacing has shown to be harmful in HF pts. Thought of moving it to a more physiological position But caution due to knock-on effects
  • LV lead could be paced from a number of different points Quadripolar leads can pace from four different sites along the LV lead – creates a huge array of different vectors (64) that can be paced from
    Doesn’t yet really improve CRT responsiveness
    but helps void diaphragmatic capture:
    As phrenic nerve runs over lateral border of pericardium If captured then pt experiences ‘hiccups’ with every paced heart beat
  • PATIENT SELECTION probably best way to optimize CRT
26
Q

What is E wave

A

passive’ ventricular filling.
Relaxation of the ventricle as it fills with blood
Note: this is not actually a passive process (sucking blood in)

27
Q

What is the A wave

A

atrial contraction, adding a little more blood

28
Q

Timing of A wave and E wave

A

These must be timed carefully to maximise efficiency
Note the dead time between e and a wave
We don’t want an overlap between the two at all as this will create an inefficiency BUT
If the time increases then there is more backflow and also more inefficiency

29
Q

Impact of a prolonged A wave

A

encroaches on systole (can take a variable amount of time), causes systole to be pushed along then encroaches on E wave
Passive filling overlapping with active filling
Increased PR interval when longer time for atrial to contract

30
Q

CRT in pts with narrow QRS

A

When CRT used in pt with narrow QRS
I.e. mechanical dyssynchrony without electrical dyssynchrony
→ DEATH rate increased
CONTRAINDICATED

BSc module 2 (4 decks)

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