Pericardial tamponade: A comprehensive emergency medicine and echocardiography review.

INTRODUCTION: Pericardial tamponade requires timely diagnosis and management. It carries a high mortality rate. OBJECTIVE: This review incorporates available evidence to clarify misconceptions regarding the clinical presentation, while providing an in-depth expert guide on bedside echocardiography. It also details the decision-making strategy for emergency management including pericardiocentesis, along with pre- and peri-procedural pearls and pitfalls. DISCUSSION: Pericardial effusions causing tamponade arise from diverse etiologies across acute and sub-acute time courses. The most frequently reported symptom is dyspnea. The classically taught Beck's triad (which includes hypotension) does not appear commonly. Echocardiographic findings include: a pericardial effusion (larger size associated with tamponade), diastolic right ventricular collapse (specific), systolic right atrial collapse (sensitive), a plethoric non-collapsible inferior vena cava (sensitive), and sonographic pulsus paradoxus. Emergent pericardiocentesis is warranted by hemodynamic instability, impending deterioration, or cardiac arrest. Emergent surgical indications include type A aortic dissection causing hemopericardium, ventricular free wall rupture after acute myocardial infarction, severe chest trauma, and iatrogenic hemopericardium when bleeding cannot be controlled percutaneously. Pre-procedure management includes blood products for patients with traumatic hemopericardium; gentle intravenous fluids to hypotensive, hypovolemic patients with consideration for vasoactive medications; treatment of anticoagulation, coagulopathies, and anemia. Positive-pressure ventilation and intravenous sedation can lower cardiac output and should be avoided if possible. Optimal location for echocardiography-guided pericardiocentesis is the largest, shallowest fluid pocket with no intervening vital structures. Patient positioning to prevent hypoxia and liberal amounts of local anesthesia can facilitate patients remaining still. Safe needle guidance and confirmation of catheter placement is achieved using low-depth sonographic views, injection of agitated saline, and evaluation of initial aspirate for hemorrhage. Pericardial fluid should be drained slowly to avoid pericardial decompression syndrome. CONCLUSION: An understanding of the pathophysiology, clinical presentation, echocardiographic findings, and time-sensitive management of pericardial tamponade is essential for emergency physicians.

Omecamtiv mecarbil evokes diastolic dysfunction and leads to periodic electromechanical alternans.

Omecamtiv mecarbil (OM) is a promising novel drug for improving cardiac contractility. We tested the therapeutic range of OM and identified previously unrecognized side effects. The Ca2+ sensitivity of isometric force production (pCa50) and force at low Ca2+ levels increased with OM concentration in human permeabilized cardiomyocytes. OM (1 µM) slowed the kinetics of contractions and relaxations and evoked an oscillation between normal and reduced intracellular Ca2+ transients, action potential lengths and contractions in isolated canine cardiomyocytes. Echocardiographic studies and left ventricular pressure-volume analyses demonstrated concentration-dependent improvements in cardiac systolic function at OM concentrations of 600-1200 µg/kg in rats. Administration of OM at a concentration of 1200 µg/kg was associated with hypotension, while doses of 600-1200 µg/kg were associated with the following aspects of diastolic dysfunction: decreases in E/A ratio and the maximal rate of diastolic pressure decrement (dP/dtmin) and increases in isovolumic relaxation time, left atrial diameter, the isovolumic relaxation constant Tau, left ventricular end-diastolic pressure and the slope of the end-diastolic pressure-volume relationship. Moreover, OM 1200 µg/kg frequently evoked transient electromechanical alternans in the rat in vivo in which normal systoles were followed by smaller contractions (and T-wave amplitudes) without major differences on the QRS complexes. Besides improving systolic function, OM evoked diastolic dysfunction and pulsus alternans. The narrow therapeutic window for OM may necessitate the monitoring of additional clinical safety parameters in clinical application.

Respiratory Fluctuation of Peak Systolic Velocities in the Carotid Doppler Waveforms of Patients With Obstructive Airway Disease: Evidence of Pulsus Paradoxus With Experimental Validation.

OBJECTIVES: To characterize fluctuations in peak systolic velocities (PSVs) in Doppler waveforms of the carotid artery in patients with and without obstructive airway disease and in volunteers subjected to incremental levels of airway resistance in an experimental model. METHODS: The PSV variation in common carotid waveforms was measured in 100 patients who had had a carotid ultrasound examination and no respiratory or carotid disease. This was compared to that of patients who had this study during an admission for acute exacerbation of chronic obstructive pulmonary disease (COPD). The PSV variation was correlated with pulmonary function testing. In addition, 14 healthy volunteers were asked to breathe through 5 resistors. Simultaneous recordings were made of Doppler waveforms in the common carotid artery, cardiac activity, and respiration. Peak systolic velocity changes from inspiration to expiration were calculated. RESULTS: Of the 100 patients without respiratory disease, the magnitude of the PSV variation averaged 6.3 cm/s. Of the 33 patients with COPD, the PSV variation averaged 16.5 cm/s. Nineteen of the 33 patients with COPD had concurrent pulmonary function testing; there was a statistically significant correlation between the PSV variation and forced vital capacity and forced expiratory volume indices. For the volunteers, mean velocity changes were 7.1, 6.6, 8.3, 15.1, and 16.1 cm/s for 0.00-, 2.15-, 3.27-, 3.58-, and 5.77-cm H2 O/L/s levels of breathing resistance, respectively. There was a statistically significant relationship between an increasing airway load and the decline in PSV during inspiration (P = .02). CONCLUSIONS: The PSV variation is greater in patients with increased airway resistance. Similar changes are evident in volunteers breathing into resistors. These findings likely reflect pulsus paradoxus.

The Use of Point-of-Care Ultrasound to Evaluate Pulsus Paradoxus in Children With Asthma.

Pulsus paradoxus (PP) is defined as a fall of systolic blood pressure of greater than 10 mm Hg during the inspiratory phase of respiration. Measurement of PP is recommended by national and international asthma guidelines as an objective measure of asthma severity but is rarely used in clinical practice. Cardiac point-of-care ultrasound with pulsed wave Doppler imaging measuring respiratory-phasic changes of mitral valve inflow velocities is well described in cardiac tamponade as "sonographic" PP. We present 10 cases of acute asthma presenting to an emergency department showing the finding of sonographic determined PP in the apical 4-chamber view of the heart on pulsed wave Doppler imaging.

Respiratory waveform variation can prevent pulsus paradoxus measurement by sphygmomanometry.

BACKGROUND: Pulsus paradoxus (PP) represents increased fluctuation of systolic pressure during the respiratory cycle. PP increases in pathologic conditions, including asthma and other obstructive airways diseases. Respiratory waveform variation (RWV) represents arterial-waveform baseline variability resulting from intra-pleural pressure changes during the respiratory cycle in the presence of airway obstruction. It is not known whether RWV influences manual PP measurement using a sphygmomanometer and stethoscope. METHODS: We performed an observational study in six healthy adults. Participants performed tidal-breathing through a breathing apparatus with pre-determined inspiratory (0-45.6 cm H2O) and expiratory (0-24.4 cm H2O) resistance levels for a total of 23 data sets per participant. PP was measured from continuous radial artery pressure recordings as the absolute difference between maximum and minimum systolic pressure levels during a complete respiratory cycle. RESULTS: In this study, PP values measured without applied airway resistance exceeded 10 mmHg, the traditional definition of PP, in five of the six participants. Manual measurement of PP would not be possible at greater RWV because the maximum diastolic pressure exceeded minimum systolic pressure during RWV. CONCLUSIONS: PP in normal adults may exceed 10 mmHg, and RWV may be of sufficient magnitude to preclude manual PP measurement.

Electrical and mechanical alternans during ventricular tachycardia with moderate chronic heart failure.

A chronic heart failure (CHF) rat underwent epicardial programmed electrical stimulation (PES). Ventricular tachycardia (VT) developed during PES. Mechanical alternans was noted despite fixed tachycardia cycle length. Anti-tachycardia pacing attempts initiated a second VT that generated pulse intermittently and then degenerated into pulseless VT with electrical alternans.To our knowledge electrical and mechanical alternans have not been recorded in animal models of CHF during VT. The distinct events of mechanical alternans and electrical alternans may be indicative of progressively worsened calcium handling in the compromised cardiomyocytes.Although ion channel differences between rodents and humans exist, this work attempts to demonstrate this rat model's usefulness in understanding cardiac electrophysiology in CHF.

Pleth Variability Index to Assess Course of Illness in Children with Asthma.

BACKGROUND: Status asthmaticus (SA) is a common reason for admission to the pediatric emergency department (ED). Assessing asthma severity efficiently in the ED can be challenging for clinicians. Adjunctive tools for the clinician have demonstrated inconsistent results. Studies have shown that pulsus paradoxus (PP) correlates with asthma severity. Pleth Variability Index (PVI) is a surrogate measure of PP. OBJECTIVE: We investigated whether PVI at triage correlates with disposition from the ED. METHODS: We recruited children aged 2-18 years old who presented to the pediatric ED of a tertiary care children's hospital with SA. PVI, Respiratory Severity Score, and vital signs were documented at triage and 2 hours into each patient's ED stay. PVI was measured using the Masimo Radical-7® monitor (Masimo Corp., Irvine, CA). RESULTS: Thirty-eight patients were recruited. Twenty-seven patients were discharged home, 10 patients were admitted to the general pediatrics floor and 1 patient was admitted to the intensive care unit. PVI values at triage did not correlate with disposition from the ED (p = 0.63). Additionally, when trending the change in PVI after 2 hours of therapy in the ED, no statistically significant patterns were demonstrated. CONCLUSIONS: Our study did not demonstrate a correlation between PVI and clinical course for asthmatics. PVI may be more clinically relevant in sicker children. Furthermore, it is possible that continuous monitoring of PVI may demonstrate more unique trends in relation to asthma severity versus single values of PVI. Additional studies are necessary to help clarify the relationship between PVI and the clinical course of children with SA.

Point-of-Care Diagnosis of Cardiac Tamponade Identified by the Flow Velocity Paradoxus.

The presentation of cardiac tamponade is a spectrum from occult to extreme. The clinical history, physical exam, electrocardiogram, and radiographic findings of tamponade have poor sensitivities and even worse specificities. We use a clinical scenario to demonstrate how point-of-care cardiac ultrasound can diagnose impending cardiac tamponade in a clinically stable patient. The ultrasound finding we recommend is the flow velocity paradoxus, in which respiratory variation causes significant changes in transvalvular inflow velocities, which are exaggerated when tamponade is present. The management of a pericardial effusion depends on its physiologic effect, and point-of-care ultrasound directly measures that effect and expedites patient care.

Relative refractoriness of left ventricular contraction underlies human tachycardia-induced mechanical and electrical alternans.

BACKGROUND: Mechanical alternans (MA) and electrical alternans (EA) are predictors of cardiac events. Experimental studies have suggested that refractoriness of calcium cycling underlies these cardiac alternans. However, refractoriness of left ventricular contraction has not been examined in patients with cardiac alternans. METHODS: In 51 patients with miscellaneous heart diseases, incremental right atrial pacing was performed to induce MA and EA. MA was quantified by alternans amplitude (AA: the difference between left ventricular dP/dt of a strong beat and that of a weak beat), and AA at 100/min (AA100) and maximal AA (AAmax) were measured. EA was defined as alternation of T wave morphology in 12-lead electrocardiogram. Relative refractoriness of left ventricular contraction was examined by drawing the mechanical restitution curve under a basal coupling interval (BCL) of 600 ms (100/min) and was assessed by the slope at BCL (Δmechanical restitution). Postextrasystolic potentiation (PESP) was also examined and the slope of PESP curve (ΔPESP) was assessed as a property to alternate strong and weak beats. RESULTS: MA and EA were induced in 19 patients and in none at 100/min or less, and at any heart rate in 32 and in 10, respectively. AA100 and AAmax correlated positively with Δmechanical restitution and negatively with ΔPESP. Patients with EA had a significantly larger Δmechanical restitution and a significantly larger absolute value of ΔPESP than those without. CONCLUSIONS: In patients with MA and EA, the left ventricular contractile force during tachycardia is under relative refractoriness and prone to cause large fluctuation of contractile force.

Pulsus Alternans in Critical Aortic Stenosis: When the Left Ventricle Is Failing.

A 58-year-old man presented with worsening dyspnea. Electrocardiogram showed variation in T-wave amplitude occurring every other beat. Transthoracic echocardiography revealed a severe aortic stenosis with beat-to-beat variation in stroke volume, suggestive of pulsus alternans. Recognition of pulsus alternans is important because it is considered a marker of poor prognosis.

Successful ß-blocker introduction under intra-aortic balloon pumping and ivabradine in a patient with new-onset dilated cardiomyopathy and pulsus alternans: a case report.

Background: Pulsus alternans has been considered a sign of poor prognosis in patients undergoing treatments for heart failure. However, it may be overlooked in patients with intra-aortic balloon pumps (IABPs). The use of IABP and ivabradine for a ß-blocker introduction in a patient with dilated cardiomyopathy (DCM) and pulsus alternans and its consequence have never been reported. Case summary: In a 16-year-old high school boy with idiopathic DCM [left ventricular end-diastolic diameter (LVDd), 72 mm; left ventricular ejection fraction (LVEF), 18%], the introduction of carvedilol therapy failed, causing cardiogenic shock under inotropes. Therefore, an IABP support was provided, and he was transferred to our hospital. The arterial pressure waveform under IABP demonstrated pulsus alternans with sinus tachycardia at 135/min. Ivabradine reduced the heart rate to ∼100/min and eliminated the pulsus alternans neither decreasing the cardiac index nor increasing the pulmonary artery wedge pressure. Subsequently, carvedilol was reintroduced, and IABP and inotropes were discontinued. Then, 112 days after his transfer to our hospital, left ventricular reverse remodelling was confirmed (LVDd, 54 mm; LVEF, 44%), and he returned to school. The carvedilol dose reached 20 mg/day in 4 months after discharge, and further improvement was observed a year after discharge (LVDd, 54 mm; LVEF, 52%). Discussion: Pulsus alternans is considered a predictor of poor prognosis. However, IABP and ivabradine may stabilize the haemodynamics in pulsus alternans, leading to a successful ß-blocker introduction.

Baseline Blood Pressure and Left Ventricular Reverse Remodeling in Dilated Cardiomyopathy with Spontaneous Mechanical Alternans.

Objective Spontaneous mechanical alternans (MA), or pulsus alternans, has been observed in heart failure patients with hypertension or tachycardia for 150 years and is considered a sign of a poor prognosis. However, in some dilated cardiomyopathy (DCM) patients with MA, optimal medical therapy (OMT) brings left ventricular reverse remodeling (LVRR), a preferable prognostic indicator. This study examined the probability of LVRR in DCM patients with spontaneous MA and whether or not LVRR can be predicted by the baseline blood pressure or heart rate. Methods We conducted a single-center, retrospective observational study of newly diagnosed DCM patients from January 2017 to December 2020. Results Thirty-three newly diagnosed DCM patients were retrospectively examined. Spontaneous MA was observed during diagnostic cardiac catheterization in at least 1 of the pressure waveforms of the aorta, left ventricle, pulmonary artery, or right ventricle in 10 patients (30%) (MA-group). LVRR after OMT was achieved roughly equally in the MA group (6 of 10, 60%) and the non-MA group (12 of 23, 52%). In the MA group, those who achieved LVRR had a significantly higher baseline systolic aortic pressure (more than 120 mmHg in all 6 patients) than those who did not, although the baseline heart rate did not show a significant correlation with LVRR. In contrast, in the non-MA group, LVRR was unrelated to the baseline aortic pressure or heart rate. Conclusion The probability of LVRR in newly-diagnosed DCM patients with spontaneous MA was similar to that in those without spontaneous MA. Spontaneous MA may not necessarily be a sign of a poor prognosis if observed in patients with a preserved blood pressure.

A Premature Ventricular Contraction Associated With Transient Worsening Pulsus Alternans: A Case Report.

Pulsus alternans is a rare condition characterized by alternation between strong and weak pulses during regular heart rhythm. Although pulsus alternans occurs mostly in severe heart failure, it can also be seen in other conditions that alternate ventricular contraction such as rapid tachycardia and extrasystole. Here, we report the case of a patient with peripartum cardiomyopathy who developed worsening pulsus alternans after a premature ventricular contraction.

Occurrence of pulsus alternans during anaesthesia of two dogs and one cat and its treatment.

The authors report the occurrence of pulsus alternans, a condition characterised by the alternance of pulses of higher and lower amplitude, in two dogs and one cat under general anaesthesia. The presence of an underlying cardiac disease was confirmed in the cat but not in either dog, which - based on history and clinical findings - had presumably normal cardiovascular function before the anaesthetic. Possible mechanisms, including negative inotropy and haemodynamic and Frank-Starling effects, as well as the role of general anaesthesia as the potential triggering factor, are discussed in this report. Ephedrine resulted in the successful treatment of pulsus alternans, as demonstrated by the return of normal pulse and synchronisation of heart and pulse rates in the cat and in one dog. In the other dog, pulse pattern and frequency returned to normal once the guidewire for central line placement was withdrawn.

Mechanism of pulsus bisferiens in thoracoabdominal thoracic aneurysms: Insights from wave intensity analysis.

Aortic pulsatile hemodynamics are important in various clinical conditions. Whereas the importance of wave reflections of the closed type in pulsatile hemodynamics has been extensively studied, less is known about the impact of reflections of the open type, in which reflected waves changes both direction and type (compression vs suction) compared to the incident wave. In this report, we present careful pulsatile hemodynamic analyses of a case in which prominent reflections of the open type occur in a patient with a thoracoabdominal aortic aneurysm, causing a highly abnormal proximal aortic and peripheral arterial hemodynamic pattern, known as pulsus bisferiens. Wave intensity analysis of central pressure-flow data demonstrated an early systolic forward-traveling compression wave followed by a prominent late systolic forward-traveling expansion wave, along with an abnormal prominent late systolic/early diastolic backward-traveling compression wave which produced a sharp rise in diastolic pressure, and was responsible for the pulsus bisferiens pattern.

Cardiotoxicity Associated with Midazolam in a Patient with Diphtheria.

BACKGROUND: Adverse cardiorespiratory events are associated with midazolam continuous IV infusion, used for sedation. HISTORY: Here we are reporting a case of 5 year old male child suffering from diphtheria induced airway obstruction, and myocarditis, who received midazolam in the form of IV infusion for sedation while undergoing mechanical ventilation for respiratory failure. Adverse Event: Six hours after starting midazolam infusion he started developing pulsus bigeminus and bradycardia and eventual death after two hours. CONCLUSION: Midazolam, although considered one of the safest drugs, need to be used cautiously in a child with myocarditis, because of the possible cardiotoxic effect in an already affected heart.

Value of measuring esophageal pressure to evaluate heart-lung interactions-applications for invasive hemodynamic monitoring.

Evaluation of intrathoracic pressure is the cornerstone of the understanding of heart-lung interactions, but is not easily feasible at the bedside. Esophageal pressure (Pes) has been shown to be a good surrogate for intrathoracic pressure and can be more easily measured using a small esophageal catheter, but is not routinely employed. It can provide crucial information for the study of heart-lung interactions in both controlled and spontaneous ventilation. This review presents the physiological basis, the technical aspects and the value in clinical practice of the measurement of Pes.

Reversed Pulsus Paradoxus in Right Ventricular Failure.

Reversed pulsus paradoxus was first described in 1973 as a rise in peak systolic pressure on inspiration in patients with idiopathic hypertrophic subaortic stenosis or isorhythmic ventricular rhythm and in patients with left ventricular systolic dysfunction on positive pressure ventilation. Positive pressure ventilation, for example, may impel blood from the pulmonary capillaries and venules into the left atrium. This may increase left ventricular preload and accelerate ventricular emptying, which in turn may cause the systolic arterial pressure to rise during inspiration. We observed this phenomenon in a patient with a large pericardial effusion, right ventricular failure, and pulmonary arterial hypertension, and we noted the lack of echocardiographic features of tamponade in the presence of right ventricular hypertrophy and pulmonary hypertension. This case report discusses the subsequent occurrence of acute congestive heart failure after pericardiocentesis.