Cardiac Resynchronisation Therapy

Question 1

When do guidelines suggest CRT is considered?

Answer 1

When patients are still symptomatic with LVEF <35% despite medical therapy with ACEi, Beta Blockers, MR antagonists and diuretics. But must have sinus rhythm and QRS duration >130ms

Question 2

What is CRT?

Answer 2

Paces the contraction and relaxation of the right and left ventricles and atria to coordinate ventricular contraction to improve cardiac output and symptoms

• Uses an extra lead in the left ventricle so that both sides are controlled simultaneously
• Inserted intraclavicularly via the subclavian artery and the LV lead is traversed down a coronary sinus to reach its destination

Question 3

What devices exist?

Answer 3

1. Rate/rhythm control using low energy pacemaker-a CRT-P
   - used to speed up bradyarrhythmias and slow tachyarrhythmias
2. Rate/rhythm control plus ICD with high energy- a CRT-D
   - used to speed/slow arrhythmias
   - defibrillates in response to persistent arryhthmia/VF

Question 4

What cut-offs do NICE use to define who receives which type of device?

Answer 4

As NYHA class increases, more likely to give CRT-P
As QRS widens, more likely to receive CRT-D
*although NYHA class 4 with QRS >150ms is CRT-P recommended-because ICD too expensive for patient with poor prognosis?

Question 5

What are the benefits of CRT?

Answer 5

• Increased left ventricular ejection fraction
• reduction in ventricular dimensions (less dilation)
• delayed symptom onset
• reduced hospitalisation for heart failure

Question 6

What are the complications of CRT?

Answer 6

Procedural complications:

• haematoma
• pneumothorax
• pericardial effusion
• infection
• air embolus
• axillary vein thrombosis

Late complications:

• Twiddler syndrome
• Infection
• box/lead erosion
• lead damage/failure
• venous obstruction
• Mortality from fitting devices is very low and only 5% chance of procedural complications

Question 7

Evidence for CRT-P use in Heart Failure:

Answer 7

MIRACLE Trial:

CRT-P shown to be significantly better than medical therapy for improving LVEF and NYHA

Question 8

Evidence against CRT-P use in heart failure:

Answer 8

MUSTIC Trial:

Showed no difference between CRT-P and medical therapy for all-cause mortality

Question 9

Evidence for CRT-D use in Heart Failure:

Answer 9

RAFT Trial:

CRT-D was shown to be significantly better than ICD alone for mortality and hospitalisation

Question 10

Evidence against CRT-D Use in heart failure:

Answer 10

PINTER Trial:
Showed no difference between CRT-D and ICD in heart failure
*No evidence to suggest CRT-D is better than ICD for SCD prevention

Question 11

Pitfalls of CRT evidence:

Answer 11

The evidence for CRT is good for patients of NYHA class >II but there is little evidence for class I despite the fact CRT could be important in Class I for delaying symptom onset and development