Use of a Non-invasive Cardiac Output Measurement in a Patient with Low-output Dilated Cardiomyopathy

Cardiac index: A superior parameter of cardiac function than left ventricular ejection fraction in risk stratification of hypertrophic cardiomyopathy

BACKGROUND

An appropriate indicator of cardiac function in the risk stratification of hypertrophic cardiomyopathy (HCM) patients is urgently needed. Cardiac index that reflects cardiac pumping function may be suitable.

OBJECTIVE

The purpose of this study was to investigate the clinical significance of reduced cardiac index in HCM patients.

METHODS

A total of 927 HCM patients were enrolled. The primary endpoint was cardiovascular death. The secondary endpoints were sudden cardiac death (SCD) and all-cause death. Combination models were constructed by adding reduced cardiac index and reduced left ventricular ejection fraction (LVEF) to the HCM risk-SCD model. Predictive accuracy was determined by C-statistics.

RESULTS

Reduced cardiac index was defined as cardiac index ≤2.42 L/min/m². During median follow-up of 4.3 years, 51 patients reached the endpoint. Reduced cardiac index independently increased the risk of cardiovascular death (adjusted hazard ratio [aHR] 2.976; P = .007), SCD (aHR 6.385; P = .001), and all-cause death (aHR 2.428; P = .010). By adding reduced cardiac index to the HCM risk-SCD model, the model C-statistic increased from 0.691 to 0.762, with an integrated discrimination improvement of 0.021 (P = .018) and a net reclassification improvement of 0.560 (P = .007). The addition of reduced LVEF failed to improve the original model. Better predictive accuracy for all endpoints was also indicated in reduced cardiac index than in reduced LVEF.

CONCLUSION

Reduced cardiac index is an independent predictor of poor prognoses in HCM patients. Combining reduced cardiac index rather than reduced LVEF improved the HCM risk-SCD stratification strategy. The reduced cardiac index showed better predictive accuracy than reduced LVEF for all endpoints.

Novel Ramp Test to Optimize Pressure Setting of Adaptive Servo-Ventilation Using Non-Invasive Lung Fluid Level Quantification

BACKGROUND Optimal patient selection and device pressure settings are key to successful adaptive servo-ventilation therapy, but there is no established strategy thus far. Adaptive servo-ventilation therapy at an inappropriately high pressure setting for those without pulmonary congestion decreases cardiac output and worsens clinical outcomes. The remote dielectric sensing system (ReDS) is a novel noninvasive tool to estimate the lung fluid amount. The ReDS might be a promising tool for successful adaptive servo-ventilation therapy if appropriately utilized for optimal patient selection and device pressure setting. CASE REPORT An 83-year-old woman was admitted to our hospital to treat acute decompensated heart failure with preserved ejection fraction that was refractory to conventional medical therapy. Following the confirmation that she had significant pulmonary congestion with 47% of the ReDS value (normal range, 20-35%), we performed a "ramp test" to optimize device pressure, by measuring ReDS values and noninvasively estimating the cardiac output and stroke volume at each pressure setting. The device pressure setting was finally determined to minimize pulmonary congestion and maximize cardiac output. Following the continuous adaptive servo-ventilation therapy with the optimized pressure setting, the patient's hospitalization was uneventful and she was discharged. CONCLUSIONS We propose performing a ramp test to optimize the pressure setting of adaptive servo-ventilation by utilizing ReDS technology for each patient, instead of using a default or inappropriately higher pressure setting. However, further studies including large patient populations are warranted to validate the prognostic implication of this customized ramp test protocol.

Usefulness of Optimization of Interventricular Delay Using an Electrical Cardiometry Method in Patients with Cardiac Resynchronization Therapy Implantation

There are no studies examining interventricular (VV) delay optimization by an electrical cardiometry method in relation to subsequent cardiac function in cardiac resynchronization therapy (CRT) -implanted patients. This study aimed to compare the VV delay in CRT-implanted patients by the dp/dt and electrical cardiometry and to examine the optimization of VV delay and improvement of cardiac function. We examined 19 consecutive CRT-implanted patients. The protocol included biventricular stimulation with either simultaneous or sequential pacing, and we evaluated systolic volume (SV) using an electrical cardiometry and the dp/dt of the left ventricle. The optimal VV delay was determined by the maximum SV using the electrical cardiometry. Two groups were defined, those whose increase in SV was at or above the median and those whose SV increase was below the median; changes in left ventricular ejection fraction (LVEF). The correlation between the VV delay optimized by the electrical cardiometry and dp/dt methods was high (R = 0.61, P = 0.006). Compared to the baseline SV (43.4 mL), the SV increased to 47.8 mL with simultaneous biventricular pacing (versus baseline P = 0.008) and further increased to 49.8 mL with optimized VV delay (versus simultaneous biventricular pacing P = 0.020). LVEF after 6 months significantly improved in the above-median SV increase group (37.6 versus 28.2%, P = 0.041), but not in the below-median SV increase group (26.5 versus 26.5%, P = 0.985). In conclusion, the optimal VV delay by electrical cardiometry method was almost concordant with that by the dp/dt method. Cardiac function significantly improved in the group with the above-median SV increase.

Doppler Echocardiography-Guided Heart Rate Modulation Therapy Using Ivabradine in a Patient with Systolic Heart Failure

Heart rate reduction using ivabradine, a selective I_f channel blocker that purely decreases heart rate without affecting hemodynamics, improves clinical outcomes in patients with systolic heart failure. However, the ideal heart rate that should be a target remains unknown. Our team recently proposed a methodology using Doppler echocardiography to estimate ideal heart rate, at which E-wave and A-wave stand adjacent without overlap. However, the implication of Doppler echocardiography-guided heart rate modulation therapy using ivabradine remains uncertain. We had a 72-year-old man with systolic heart failure and sinus tachycardia who initiated ivabradine therapy. Ivabradine dose was adjusted between 5.0 mg/day and 10.0 mg/day and continued for 12 weeks to minimize the overlap between the two echocardiography waves, accompanying improvement in cardiac output, left ventricular ejection fraction, plasma B-type natriuretic peptide, and six-minute walk distance. Doppler echocardiography-guided heart rate regulation therapy using ivabradine may be a promising strategy to improve cardiac function and clinical outcomes in patients with systolic heart failure, although further studies are required to validate this hypothesis.

Adaptive Servo-Ventilation as a Novel Therapeutic Strategy for Chronic Heart Failure

The introduction of new therapeutics for patients with chronic heart failure, including sacubitril/valsartan, sodium-glucose cotransporter 2 inhibitors, and ivabradine, in addition to beta-blockers, angiotensin converting enzyme inhibitors, and mineralocorticoid receptor antagonists, lends an opportunity for significant clinical risk reduction compared to what was available just one decade ago. Further clinical options are needed, however, for patients with residual clinical congestion refractory to these therapies. Adaptive servo-ventilation is a novel therapeutic option to address significant clinical volume in cases resistant to medical therapy. The aggregate benefit of these additional therapeutic strategies in addition to foundational medical therapy may be a promising option in the selected candidates who do not achieve acceptable clinical and quality-of-life improvements with oral medical therapy alone. Now is the era to reconsider the implication of an adaptive servo-ventilation-therapy-incorporated medical therapeutic strategy for patients with congestive heart failure.

Optimal Heart Rate Modulation Using Ivabradine

Heart rate modulation therapy using ivabradine improves mortality and morbidity in patients with systolic dysfunction. However, a target heart rate remains uncertain. Echocardiography-guided ivabradine therapy, in which we attempt to approach zero overlap between two diastolic filling inflow waves, has recently been proposed to maximize cardiac output, facilitate reverse remodeling, and reduce mortality and morbidity, instead of using an absolute value for the target heart rate. Prospective studies are needed to validate the clinical implication of these therapeutic strategies. Also, this concept should be expanded to other clinical scenarios.

Safety Monitoring for Obstructive Hypertrophic Cardiomyopathy During Exercise

Patients with hypertrophic cardiomyopathy (HCM) are prohibited from engaging in intensive exercise, to avoid sudden death. Given that patients with HCM, even those without left-ventricular outflow tract obstruction at rest, potentially have exercise-induced obstruction, reasonable monitoring methods during exercise are required. We present the case of a woman with HCM with exercise-induced obstruction whose hemodynamics during stress echocardiography were under observation using noninvasive cardiac output monitoring. Stroke volume declined during exercise before the manifest elevation of the left-ventricular outflow tract pressure gradient. As shown here, a noninvasive monitoring method can be useful in monitoring hemodynamics during exercise in HCM patients.