Heart II

Learning objectives

Evaluate LV and RV function qualitatively (LV enlargement and decreased systolic function, LA enlargement, RV enlargement)
Identify pericardial effusion and inferior vena cava collapsibility
Learn the limitations of focused cardiac ultrasound

Key points

Qualitative assessment of LV systolic function should be categorized as:
- 1. Hyperdynamic
- 2. Normal
- 3. Reduced
- 4. Severely reduced
Determination of LV diastolic function, regional wall motion abnormalities, and structural abnormalities requires additional training.
The objective of RV assessment is to evaluate for acute RV failure caused by an increase in pulmonary pressure or direct right ventricular injury.
RV failure can be recognized by qualitative analysis of size, function, and interventricular septal kinetics.

LV function Evaluation

This module will focus on basic image interpretation for cardiac POCUS (also called FOCUS - Focused Cardiac Ultrasound or goal directed-echocardiography).

The definition of FOCUS includes the following features:

-Goal-directed and problem oriented

-Limited in scope and simplified

-Time sensitive and repeatable

-Qualitative or semiquantitative

-Performed at the point of care by clinicians

How can we assess LVEF qualitatively?

Always attempt to assess from multiple views
We will learn 2 methods in this module:
- Fractional shortening method
- E-point septal separation (EPSS)

Fractional shortening method

A decrease of linear LV diameter by 1/3 or more correlates with normal EF
The preferred view for this method is the PSAX view at the level of the papillary muscles (mid-ventricular view)
- In this view endocardial excursion and myocardial thickening are assessed
- Imagine a fictional point in the center of the ventricle (to aid this one can place a finger in the middle of the ventricle) and the reduction of LV diameter is closely observed

Normal EF: PSAX

Mitral valve level and then papillary muscle level is seen. All walls of the LV seem to be contracting symmetrically and LV diameter is decreased by more than 1/3.

(Placing a finger in the middle of the ventricle can help)

Reduced EF: PSAX

PSAX from a patient with non-ischemic cardiomyopathy and a severely reduced EF.

EPSS was measured as 2.1 cm (see EPSS method below).

Hyperdynamic LV: PSAX

Almost complete obliteration of LV cavity is seen in this patient which is indicative of a hyperdynamic LV.

Hypertrophy and dilated cardiomyopathy can be inferred by abnormal wall thickness (septum or free wall) and end-diastolic diameter (measured at level of mitral tips).

Normal LV end-diastolic wall thickness is 6 to 12 mm.
Normal LV end-diastolic diameter is 40 to 60 mm (correlates with height).

E-point septal separation (EPSS) method

This method requires the PLAX view and M mode
Under M mode align the line to the tip of the MV. One has to be careful to align the view as best as possible to avoid overestimation of the EF
Measure the minimum distance between the anterior leaflet of the mitral valve and septum.

M-Mode showing an EPSS of 18 mm showing probably decreased EF

Interpretation

<7 mm: Normal LVEF

7–10 mm: Borderline/unclear

>10 mm: Probably decreased LVEF (or valvular disease)

Severely reduced EF

A dilated LV and an increased distance of the anterior leaflet of the MV and interventricular septum is seen

Hypertrophic cardiomyopathy

Almost complete obliteration of the LV cavity with anterior leaflet of MV almost touching the interventricular septum

NEJMdo005614_download.mp4

Focused Cardiac Ultrasonography for Left Ventricular Systolic Function

NEJM video that summarizes the concepts mentioned here and mentions additional ways of assessing LV function.

https://www.nejm.org/doi/full/10.1056/NEJMvcm1802841?query=TOC

RV function Evaluation

The RV free wall is normally thinner than the LV free wall
The RV chamber size should be approximately 2/3 the size of the LV chamber
RV normally has a crescent shape when viewed from the PSAX or triangular when viewed from an A4C view

Signs of pressure or volume overload:

RV dilation greater than LV diameter (A4C)
Flat septum/D-sign (PSAX)
RV violates rule of one-thirds (PLAX)
Paradoxical septal motion (septum bulges into LV in diastole)
Decreased tricuspid annular plane systolic excursion (TAPSE) (advanced)
RV diastolic thickness >5 mm suggests hypertrophy from chronic process, while thickness <5 mm suggests an acute process, such as pulmonary embolus (PE)
McConnell's sign: RV free wall hypokinesis with apical sparing is seen in both acute and chronic RV failure. In other words, the apex is the only area of the RV that is truly moving . The apex may be seeing move up and down like a trampoline.

Septal flattening (D-sign) and paradoxical septal motion noted on PSAX. Note the RV dilation. A pericardial effusion can also be seen around the LV.

Note the RV appears bigger than LV on this A4C. RA is also dilated. Paradoxical septal motion can also be seen with the septum bulging into the LV.

A pericardial effusion is seen as well.

Pericardial Effusion

Evaluation of pericardial effusion versus cardiac tamponade:

Pericardial effusions are best seen in subxiphoid view, but attempt to evaluate in all views.
In PLAX, pericardial effusions appear between heart and descending aorta, while pleural effusions extend behind aorta

Look for signs of tamponade physiology
- IVC plethora (most sensitive)
- RV diastolic collapse (most specific)
- RA diastolic collapse (intermediate sensitivity and specificity)
- MV or TV inflow velocity variation (an advanced technique)
Epicardial fat can mimic a pericardial effusion, but is usually located just in front of the RV, and is often more echogenic than simple fluid

Chronic pericardial effusion

Cardiac tamponade: A moderate pericardial effusio is seen associated with RV collapse

IVC Interpretation

IVC interpretation:

Easy to obtain but challenging to interpret. The ability of the IVC to predict volume responsiveness is limited except at the extremes which are:
- A collapsed [<10 mm] IVC
- A very plethoric [>2.5 cm and unchanging] IVC)
The most common serious error in IVC assessment is failure to identify a slit-like IVC and substituting the aorta.
- If only one vessel is seen in the transverse plane, then it is the aorta and the IVC is probably critically underfilled.
In spontaneously breathing patients, the IVC will collapse with inspiration, while in patients on positive pressure ventilation, the IVC will distend with inspiration.
In ventilated patients the diagnostic performance is controversial and depends on tidal volume, respiratory effort, and abdominal pressure.

RAP=Right atrial pressure

This is a general rule of thumb correlating IVC diameter and collapse during the respiratory cycle to central venous pressure .

This correlation will not apply if there are large swings in intrathoracic pressure or if the patient is on a ventilator with high levels of positive end-expiratory pressure.

Plethoric IVC (e.g. in a patient with acutely decompensated heart failure)

Slit-like IVC in a hypovolemic patient