Description

Background

Heart Failure

Approximately 600,000 Canadians are living with heart failure (HF) with 50,000 new patients diagnosed each year. Once diagnosed, the median survival for HF patients is 1.7 years for men and 3.2 years for women. As HF progresses, patients experience a worsening in symptom severity, functional capacity, and quality of life. In addition, acute exacerbations of HF is the most frequent cause of unscheduled hospital admissions. Almost 83% of all HF patients will be hospitalized at least once and 43% hospitalized more than three times. However, the mechanisms of HF decompensation are still unclear.

Most drugs (ACE-I/ARB/beta-blockers/MRA) used for the treatment of HF are prescribed because of their ability to improve symptoms or survival. The target doses of these drugs are generally selected on the basis of reported results from randomized controlled trials rather than changes produced in cardiac monitoring of hemodynamics. Interestingly, hemodynamic monitoring has been reportedly indicated in patients where it is difficult to determine their volume status, in addition to those patients refractory to therapy. The ACC/AHA 2013 guidelines3 define the importance of invasive hemodynamic monitoring in patients with:

• severe clinical decompensation in which therapy is limited by elevated filling pressures, hypoperfusion, and vascular tone
• persistent severe symptoms despite a trial of recommended therapies
• the needed or dependency for (or escalation of) pressor and inotropic therapy

Cardiogenic shock

Cardiogenic shock (CS) is a state of profound HF resulting in peripheral organ hypoperfusion, injury and failure. The precipitating events leading to CS are diverse. Patients may experience CS as a slow progression of chronic HF. More frequently however; patients experience CS after an acute cardiac insult such as an acute myocardial infarction, myocarditis or malignant ventricular arrhythmia. It is inevitable that patients who develop CS will die if treatment is not initiated rapidly. In addition, if initial medical therapy fails to maintain adequate cardiac output, initiation of mechanical circulatory support (MCS) represents a life-saving strategy. There has been no established role for the use of invasive hemodynamic measurements in the management of patients with HF. And yet, patients with CS being considered for cardiac transplantation or placement of an MCS device are required to undergo right-heart catheterization using pulmonary artery catheter (PAC), including an assessment of right heart filling pressures, pulmonary artery pressures, left heart filling pressures and cardiac output.

University Health Network (UHN) has the largest and most comprehensive MCS program in Canada. As clinicians working at the Peter Munk Cardiac Centre (PMCC) we are caring for an ever-increasing number of patients with profound refractory cardiogenic shock who require invasive hemodynamic assessment.

Rationale for the study

The majority of patients who present to the CICU require invasive hemodynamic assessment as part of their usual care. To assist in the management of these critically ill patients, the investigators need a complete understanding of the hemodynamic status. Currently, this is usually done invasively by placing a PAC. Alternatively, a non-invasive assessment using transthoracic echocardiography (TTE) can be pursued.

Pulmonary artery Catheter

In early retrospective registries, there was no benefit shown for the use of PAC. However, this had not been studied in patients with CS until recently. In a large retrospective study of CS patients, the use of PAC was associated with improved survival (30% vs 38%). This study provided the basis for the incorporation of PAC into CS treatment algorithms. In addition, the guidelines and scientific statements limited recommendations regarding PAC to use in patients with CS. The hemodynamic data obtained with a PAC can facilitate clinical decision-making and allow customization of a treatment plan through the optimization of medical therapy. However, as with any invasive diagnostic tool, the benefit must be balanced against risks. Complications of PAC include central venous access-related adverse events (<3.6%), arrhythmias and heart block (0.3% to 3.8%), and pulmonary artery rupture (0.02% to 0.03%).

Transthoracic echocardiography

TTE is a non-invasive ultrasound-based diagnostic tool that has the ability to also evaluate and track both RV and LV hemodynamic status. There is conflicting evidence of the utility of TTE monitoring in reflecting the hemodynamic changes in PAC-derived hemodynamic measurements.

Lung Ultrasound (LUS)

LUS allows for a rapid point-of-care evaluation of a number of conditions, including pulmonary edema, lung consolidation, pleural effusion, and pneumothorax. High intra-rater and inter-rater reproducibility, ease of learning, short exam duration (<5 min), and the noninvasive nature of this technique makes it an advantageous point-of-care tool. LUS is increasingly used in the acute care setting, and has improved diagnostic accuracy compared with clinical assessment and chest radiography for the identification of a cardiac aetiology in patients presenting to the emergency department with undifferentiated dyspnea. Quantification of B-lines (vertical artefacts that result from an increase in interstitial density) has been shown to be useful for the diagnosis, monitoring, and risk assessment of patients with known or suspected ADHF. Either curvilinear or phased array transducers can be used, typically at an imaging depth of 14-18 cm.

Hypothesis

The investigators hypothesize that non-invasive hemodynamic parameters derived from TTE would be comparable to those obtained invasively by PAC in patient admitted to the CICU. The investigators also hypothesize that there will be a strong correlation between intracardiac pressures and the severity of pulmonary congestion as evaluated by LUS.