Academic literature on the topic 'Arrhythmia Heart Heart Nonlinear functional analysis'

Heart failure (HF) has turned into an increasing global socioeconomic issue associated with a high morbidity and mortality. Cardiac radionuclide imaging offers important clinical information for risk stratification and tailored treatment strategies in patients with HF. Ischaemic cardiomyopathy is the most common cause of HF. Left and right ventricular function can be assessed and quantified with radionuclide ventriculography (RNV) or gated scintigraphic studies. Additionally, radionuclide imaging may help to assess functional and metabolic integrity of dysfunctional myocardium. Chronic myocardial ischaemia can lead to variable reversible states of contractile impairment termed myocardial stunning or hibernation. Radionuclide techniques including positron emission tomography with ¹⁸F-fluorodeoxyglucose or myocardial perfusion scintigraphy can identify viable myocardium with the potential for functional recovery, and thereby guide revascularization procedures. Increased sympathetic myocardial innervation assessed by ¹³¹I-metaiodobenzylguanidine (MIBG) single-photon emission tomography (SPECT) is associated with poorer HF outcomes and higher rates of sudden cardiac death or arrhythmia. Finally, left ventricular mechanical dyssynchrony can be evaluated using Fourier-transformed phase analysis of RNV or gated myocardial perfusion SPECT. This approach could potentially be useful to guide targeted resynchronization therapy in the future.

The autonomic nervous system consists of three divisions: the sympathetic (thoracolumbar), parasympathetic (craniosacral), and enteric nervous systems. The sympathetic and parasympathetic autonomic outflows involve a two-neuron pathway with a synapse in an autonomic ganglion. Preganglionic sympathetic neurons are organized into various functional units that control specific targets and include skin vasomotor, muscle vasomotor, visceromotor, pilomotor, and sudomotor units. Microneurographic techniques allow recording of postganglionic sympathetic nerve activity in humans. Skin sympathetic activity is a mixture of sudomotor and vasoconstrictor impulses and is regulated mainly by environmental temperature and emotional influences. Muscle sympathetic activity is composed of vasoconstrictor impulses that are strongly modulated by arterial baroreceptors. Heart rate is controlled by vagal parasympathetic and thoracic sympathetic inputs. Vagal influence on the heart rate is strongly modulated by respiration; it is more marked during expiration and is absent during inspiration. This is the basis for the so-called respiratory sinus arrhythmia, which is an important index of vagal innervation of the heart. Power spectral analysis of heart rate fluctuations allows noninvasive assessment of beat-to-beat modulation of neuronal activity affecting the heart. Arterial baroreflex, cardiopulmonary reflexes, venoarteriolar reflex, and ergoreflexes control sympathetic and parasympathetic influences on cardiovascular effectors. The main regulatory mechanism that prevents orthostatic hypotension is reflex arterial vasoconstriction in the splanchnic, renal, and muscular beds triggered by a decrease in transmural pressure at the level of carotid sinus baroreceptors.