[To the centennial of Norman Holter (1914-1983)].

The article is devoted to the centennial of the founder of ambulatory ECG monitoring Norman Jeffrey Holter (1914-1983). It contains brief history of the scientist's family, and depiction of his own educational way from magister of chemistry and physics to specialist in nuclear research. His activity during World War II, research related to impact of nuclear tests on environment after the war is also described. The fact is stressed that N. Holter was organizer and first president of Society of Nuclear Medicine. But most prominent contribution of N. Holter was elaboration of the method of long-term ECG monitoring of freely active patients--the method which was later named Holter Monitoring (HM). The article also contains data of first clinical trials of HM systems and stresses contribution of Holter team-mates and colleagues (B. Del Mar, G. Kennedy, S. Stern and others) in their conduct. It shows technical and ideological evolution of HM systems from large apparatuses weighting 40 kg to modern portable devices capable of collecting, storing and processing huge amounts of information, transmitting it over internet to any distance. Nontriviality and serendipity of N. Holter's approach to obtaining novel unpredictable knowledge allowed him to realize his numerous talents and abilities.

Ambulatory electrocardiology.

About 50 years ago, Norman Jefferis Holter invented a device that opened the possibility of recording heart activity over long periods of time. This invention, together with the rapid developments in electronics, has enabled a revolutionary change in the diagnosis and management of cardiac diseases. Ambulatory cardiac monitors have decreased in size to the point of becoming wearable or implantable and are able to monitor heart activity for months or even years. In addition, new telecommunication systems allow clinicians to remotely access cardiac events and to respond within a short period of time. Novel advances in computing and algorithm development are expanding the clinical applications of ambulatory devices with more complex automatic interpretation of the electrocardiographic signal. This article reviews the state of the art of these techniques from both clinical and technical approaches, covering a historic perspective up to today, and discusses current applications, challenges, and future directions.

[Long-term electrocardiogram]. / Dlouhodobý elektrokardiogram.

The review deals with the technical and clinical advances achieved in the field of long-term electrocardiography over the past decades, and outlines possible future developments. The technological background is reviewed from the initial conception by Dr Norman J Holter up to the modern loop and implantable recorders. The contemporary clinical applicability is considered including arrhythmia monitoring, tracking the morphological electrocardiographic changes with particular attention to ischaemia monitoring, and high-precision electrocardiographic measurements related to the assessment of drug-induced myocardial repolarisation changes. The section on future outlook discusses the possibility of using long-term electrocardiograms for identification of patients at increased risk of sudden arrhythmic death that might be preventable by prophylactic use of implantable defibrillators.

Heart attacks, heart rate, and gel electrodes: the invention of ambulatory cardiology.

Ambulatory cardiology began in 1959 in a department of pathology to answer a question raised at the autopsy table: are high heart rates in apparently healthy individuals a risk factor for developing coronary artery disease? This question led to the development of a miniature monitor and a new kind of electrode, which enabled clinicians to measure EKG signals during activity and over prolonged periods of time. These electrodes are now used universally for diagnosis and for monitoring the heart during a myriad of different activities and circumstances. The story of the development of the monitor and electrodes illustrates the ways in which ideas and discovery lead to applications and advances in medicine.

The history, science, and innovation of Holter technology.

Holter technology has endured for more than 40 years, and proven to be a valuable adjunctive noninvasive diagnostic technology to record the ambulatory or long-term electrocardiogram in the study of living creatures. During this span of time, many scientists, physicians, and innovators contributed to the development and evolution of Holter technology. This essay seeks to document a view of the history and evolution of the technology during that time, and concomitantly give recognition to the scientists, physicians, and engineers who contributed so greatly.

The triangular wave test for electrocardiographic devices: a historical perspective.

Baseline wander makes interpretation ECG recordings difficult, especially the assessment of ST deviation. Eliminating baseline wander without distorting the ST segment is a problem. The traditional high pass filter with a 0.5 Hz low frequency cutoff effectively suppresses baseline but introduces considerable distortion in the level of the ST segment. This distortion results from phase nonlinearities that occur when frequency content and wave amplitude change abruptly, as occurs where the end of the QRS complex meets the ST segment. Since the 1980s nonlinear, digital filters have been designed that can increase the low frequency cutoff without the introduction of phase distortion. The triangular wave test, first described in the 1990 AHA Recommendations, is an objective method for measuring the ability to suppress baseline wander without affecting the ST segment. This methodology was adopted in 3 American National Standards.

Eletrocardiograma de longa duraçäo: o sistema holter - parte II / Long-term electrocardiographic recording: the holter system. Part II

A eletrocardiografia ambulatorial é um método näo-invasivo utilizado na prática clínica para detectar, documentar e caracterizar ocorrências de comportamento anormal da atividade elétrica cardíaca durante as atividades diárias rotineiras. Como tais anormalidades ocorrem raramente, o eletrocardiograma deve ser registrado por longos períodos de tempo. Desde a introduçäo em 1961 por Norman Holter, os sistemas de eletrocardiografia ambulatorial tem sido desenvolvlidos com uma ampla variedade de fidelidade de registro, peso e tamanho dos equipamentos, capacidades de análise e formatos de relatórios. Existem três tipos básicos de gravadores: gravadores contínuos, intermitentes (gravador de eventos) e gravadores de análise em tempo real. Gravadores contínuos possuem um gravador analógico para capturar o eletrocardiograma continuadamente e tipicamente registram na fita dois ou três canais do eletrocardiograma por 24 horas. Gravadores intermitentes registram somente um limitado número de curtos segmentos de dados; sua proposta é a de capturar o comportamento elétrico anormal quando o paciente apresenta o sintoma para o qual o estudo foi indicado. Os registros intermitentes podem ser transmitidos por telefone no momento da ocorrência do evento, ou os dados podem ser armazenados e transmitidos posteriormente. Os gravadores com análise em tempo real avaliam o eletrocardiograma continuamente. Os sinais eletrocardiográficos recebidos, ao invés de serem armazenados em uma fita analógica, säo digitalizados e armazenados em memória sólida. Utilizando-se do sistema Holter, podemos também investigar arritmias, efeito terapêutico de drogas ou procedimentos, marcapassos e desfibriladores, doença cardíaca isquêmica e variabilidade da frequência cardíaca. As indicaçöes gerais para a eletrocardiografia ambulatorial seguem as recomendaçöes da Força Tarefa ACP/ACC/AHA e säo discutidas neste artigo.

Eletrocardiograma de longa duraçäo: o sistema Holter - parte I / Long-term electrocardiographic recording the holter system - part I

A eletrocardiografia ambulatorial é um método näo-invasivo, utilizado na prática clínica para detectar, documentar e caracterizar ocorrências de comportamento anormal da atividade elétrica cardíaca durante as atividades diárias rotineiras. Como tais anormalidades ocorrem raramente, o eletrocardiograma deve ser registrado por longos períodos de tempo. Desde a introduçäo, em 1961, por Norman Holter, os sistemas de eletrocardiografia ambulatorial têm sido desenvolvidos com uma ampla variedade de fidelidade de registro, peso e tamanho dos equipamentos, de capacidade de análise e de formato de relatórios. Existem três tipos básicos de gravadores contínuos, intermitentes (gravador de eventos) e gravadores de análise em tempo real. Os contínuos possuem um gravador analógico para capturar o eletrocardiograma continuadamente e tipicamente registram na fila dois ou três canais do eletrocardiograma por 24 horas. Os intermitentes registram somente um número limitado de curtos segmentos de dados; sua proposta é capturar o comportamento elétrico anormal quando o paciente apresenta o sintoma para o qual o estudo foi indicado. Os registros intermitentes poden ser transmitidos por telefone no momento da ocorrência do evento, ou os dados podem ser armazenados e transmitidos posteriormente. Os gravadores com análise em tempo real avaliam o cardiograma continuamente. Os sinais eletrocardiográficos recebidos, ao invés de serem armazenados em uma fita analógica, säo digitalizados e armazenados em memória sólida. Utilizando o sistema Holter, podemos também investigar as arritmias, o efeito terapêutico de drogas ou procedimentos, marcapassos e desfibriladores, a doença cardíaca isquêmica e a variabilidade da frequência cardíaca. As indicaçöes gerais para a eletreocardiografia ambulatorial seguem as recomendaçöes da Força Tarefa ACP/ACC/AHA e säo discutidas neste artigo.

Historical vignette celebrating the 30th anniversary of diagnostic ambulatory electrocardiographic monitoring and data reduction systems.

The ambulatory electrocardiographic (ECG) monitor is a device developed approximately 30 years ago to detect, locate and document hemodynamic insufficiency states in target organs with compromised regional arterial circulations. These insufficiency states are usually silent until they are suddenly precipitated by secondary remote, hemodynamically significant cardiac arrhythmias, hypotensive states caused by internal hemorrhage or reduced cardiac output including cardiogenic shock. Insufficiency events cause serious regional dysfunction, resulting in transitory or permanent damage of the remote target organs (brain, heart, splanchnic and renal) often causing paralytic ileus, gangrene of the gut or rectum, myocardial infarction or cerebral stroke. Comprehensive experimental studies conducted in the author's laboratory over a period of years (1946-1971) proved that such remote ischemic states are often recurrent and can cause serious, irreparable damage, but whenever the cause of the regional ischemic state was treated promptly it could reverse the insufficiency state. Practical ambulatory ECG diagnostic monitors and data reduction systems were developed to diagnose these elusive precipitating pathophysiologic events that might coincide with the patient's symptoms and thus determine the most appropriate preventive therapy.