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Bay Four

          Patterns, pearls and practical medicine

Cardiological investigations

The echo (for the amateur)

  • GIRFT have 3 categories of prioritisation for inpatient echo
      • Cat 1 – within one hour
          • Clinical tamponade (eg known effusion, post coronary intervention or PPM placement)
          • Chest pain with haemodynamic instability (incl aortic dissection if doesn’t delay CT)
          • Suspected IE with complications (eg acute HF, valve decompensation, root abscess)
          • Cardiogenic shock or ROSC
          • Suspected PE in unstable patient (esp if deciding to thrombolyse)
      • Cat 2 – within 24 hours
          • New diagnosis of HF, with no echo in the last year, and unstable or decompensated. Or acute pulmonary oedema
          • Acute MI (esp if complications)
          • PE with CV compromise post initial tx
          • Pre-angiogram or PPM insertion
          • Pre-op non-cardiac surgery if undiagnosed cardiac condition suspected (and will alter anaesthetic approach)
          • Malignant arrhythmia
          • IE with some instability
      • Cat 3 – within 5 days
          • New diagnosis of HF with no recent echo, stable and compensated
          • Syncope with systolic murmur or arrhythmia
          • Stable ACS
          • Suspected IE
  • When not to bother
      • Echo is probably overused, which delays scan for those who need it most. British society of echocardiography have guidelines on specific indications
      • Not required if:
          • Clearly end of life, or with advanced frailty and echo very unlikely to impact management
          • Unlikely to tolerate
          • SOB or oedema, with NT-Pro BNP <400 ng/L (unless other causes have been considered and excluded, or a diagnosis other than HF suspected)
          • Unchanged murmur in an asymptomatic person with a previous normal echo
          • Likely vasovagal syncope (with precipitant) and normal ECG
          • Palpitations without ECG proof of arrythmia or clinical suspicion of structural HD
          • Follow up of mild MR, AR, TR or PR (with structurally normal valves and aortic root <40mm)
          • Confirmed acute PE with no CV compromise or high-risk features
          • Routine pre-op (see peri-op medicine for some indications)
  • What to eyeball
      • Four windows
          • Parasternal long axis view – good view of LR, RV,
          • Parasternal short axis – good view of LV
          • Apical 4 chamber – best for pericardial fluid
          • Subcostal 4 chamber – can assess the IVC
      • Pay attention to
          • Chamber sizes
          • RV function (via surrogates like TAPSE or RVFAC)
          • LV function (EF, should be 55-60%)
          • E/A ratio (a measure of diastolic function)
          • RV volume
          • TAPSE (longitudinal function of RV)
          • Valves
          • Pulmonary artery systolic pressures (abnormal if > 20)
          • Other stuff (effusions, collapsibility of the IVC etc)
      • Important pathology
          • LV dilatation (End diastolic internal diameter >6.5cm)
          • RV dilation (RV area >2/3 size of LV)
          • Ventricular dysfunction reduction in wall thickening and motion, TAPSE, MAPSE
          • Regional wall motion abnormalities (RWMA)
          • Features of low venous return – small collapsing IVC, small hyperdynamic LV and RV, papillary apposition in systole
          • Pericardial collection
          • Pleural collection
          • Infective endocarditis and valvular lesions
      • Measuring systolic function
          • Cut offs often change, and can be different internationally, but currently normal EF >55% (grey zone 50-55%)
          • GLS (global longitudinal strain), measures shortening of LV and is an earlier marker of LV dysfunction (before EF goes down). If normal EF, and abnormal GLS, probably not the reason they’re in hospital, but useful
          • Certain patterns in GLS can help identify HCM, amyloid, Fabry’s, HTN, athlete’s heart
          • EF is not very precise and not static, there is variability (esp if over or under filled). And it’s artificially inflated if significant MR.
      • Measuring diastolic dysfunction
          • Normal (previously labelled grade 1 diastolic dysfunction is normal in older people)
          • Impaired diastolic function with normal filling pressures – can be HFpEF if clinical picture fits
          • Impaired diastolic function with elevated filling pressures – likely HEpEF
  • Few tips
      • Useful for unwell patients – esp in the diagnosis of shock (differentiating types), acute SOB, peri-arrest (eg too sick for CTPA). See POCUS
      • POC echo can also improve patient flow and discharge rates
      • Confirming pathology in different planes increases accuracy
      • You need to know when an image is not good enough to be interpreted – may be an issue in unwell patients or those with a big habitus
      • Echo assessment of the RV is challenging due to its complex geometry, imaging constraints, and the high dependency on loading conditions. If accurate assessment of RV is required for decision-making, consider CMR

Cardiac MRI (CMR)

  • T2-weighted imaging best for detecting inflammation and oedema while T1-weighted imaging best for evaluating chronic structural changes, fat, fibrosis, and scar tissue
  • Late gadolinium enhancement or LGE (gadolinium is an extracellular contrast agent) is a technique used for cardiac tissue characterisation eg the assessment of myocardial scar formation and regional myocardial fibrosis
  • LGE patterns
      • Mesocardial
          • HCM, DCM, pulmonary HTN
      • Patchy
          • Sarcoid, amyloid, myocarditis
      • Subendocardial
          • Infarction, amyloid, hypereosinophilia, histiocytoid cardiomyopathy, cardiac transplant
          • Can detect subtle subendocardial infactions
      • Subepicardial
          • Myocarditis (most common), sarcoid
      • Transmural
          • Infarction (most common), severe myocarditis, chronic sarcoid
  • Cardiac MRI has a high sensitivity for detecting LV thrombus (around 88%, whereas echo has 25% and TOE 40% and contrast echo 61%)
  • Also useful for differentiating athletes’ heart with LV hypertrophy from HCM (by T1/ECV mapping)
  • May not be possible to perform if implanted devices or patient claustrophobic

Ambulatory ECG monitoring

  • The Holter
      • 3 leads and a box
      • Fairly cheap (around £140)
      • Can do for different amounts of time – 24 hrs, 48 hrs, 72 hrs, 5 days, 7 days
      • Patient can keep a diary if requested to investigate symptoms
      • Indications
          • Daily or most-day palpitations to help define cause
          • To quantify ectopic burden
          • Unexplained syncope/pre-syncope (although low yield if symptoms infrequent)
          • Cryptogenic stroke to detect paroxysmal AF (might do for 2 weeks in this instance)
          • Risk stratification in HCM (looking for runs of VT)
          • Occasionally done in permanent AF (to ensure they on right rate control meds). Occasionally also done to define AF burden but not routine
  • Longer monitoring
      • Consider 2-5 day Holters, ILR or patch monitors (up to 2 weeks) as alternatives if symptoms less frequent
      • Ziopatch is often used for 2 weeks. Not always available. Bit more expensive (£265). Often used in cryptogenic stroke
      • ILRs (implantable loop recorders) are more expensive and invasive, but often diagnostic. Used if very infrequent symptoms and high burden of suspicion. Parameters can be set and device can be triggered in certain situations – sending a report to electrophysiology. Can be patient initiated too if symptoms occur.
  • Some possible findings
      • Runs of SVT or VT – d/w cardio
      • Ventricular ectopics – see palpitations, ectopics and channelopathies
      • Bradyarrthymias
          • d/w cardio if 2nd degree Mobitz type 2 or 3rd degree heart block, symptomatic severe bradycardia, pauses > 6 seconds
          • Consider OSA if mainly nocturnal bradycardia – 20% of severe OSA develop heart block and CPAP can prevent it (1st line rather than PPM) in 85% of patients if OSA the main cause
          • Sinus node disease may manifest as inappropriate sinus bradycardia, sinus pauses, tachy-brady syndrome (fast AF, but bradycardic when in SR due to rate control), chronotropic incompetence. Often only treat if symptomatic – so symptoms key in defining next steps.
      • Pauses
          • Defined as > 3 seconds
          • Need 6-7 sec pause to cause syncope
          • Can ignore if up to 3 seconds (and in AF 3-5 seconds can be normal)
          • Even long pauses are not necessarily an indication to pace if they occur in sleep (and so by definition, asymptomatic). But consider OSA.
          • Pauses > 6 seconds often require PPM
  • Intermittent ambulatory ECG monitoring
      • Can be useful to investigate symptoms but only if someone gets warning (not for sudden syncope)
      • Smart watches (eg Apple)
          • 1 lead ECG capability, intermittent monitoring of rhythm
          • Still lots of false positives. About a third of patients with irregular pulse alert get diagnosed with AF
      • Kardia AliveCor
          • Apply fingers to a pad
          • Clinically validated and reasonable quality ECG
          • Costs about £80 (patient expense)
          • Can advise patients to invest in cases of non-daily palpitations if they don’t want to wait for investigation
          • Needs to be able to use an app on smartphone alongside their device
          • If palpitations likely anxiety-induced, could potentially increase health anxiety
  • For Cardiopulmonary exercise test, Dobutamine stress echo, Technetium stress perfusion scan, CT angiogram (CTCA), 18F-FDG Cardiac PET-CT – see Chronic Coronary Syndromes

 

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