Recent diagnostic criteria have been published out of the Arrhythmia Research Laboratory at the University of Ottawa Heart Institute from Drs. Michael H Gollob and Jason D Roberts.

The Short QT Syndrome diagnostic criterion is based on a point system as follows:

QTc in milliseconds

Jpoint-Tpeak interval

Clinical History

Family History

Genotype

Patients are deemed high-probability (> or equal to 4 points), intermediate probability (3 points) or low probability (2 or less points).

In terms of the diagnosis of Romano–Ward syndrome the following is done to ascertain the condition(the "Schwartz Score" helps in so doing):

- Exercise test

- ECG

- Family history

The diagnosis of LQTS is not easy since 2.5% of the healthy population has prolonged QT interval, and 10–15% of LQTS patients have a normal QT interval. A commonly used criterion to diagnose LQTS is the LQTS "diagnostic score", calculated by assigning different points to various criteria (listed below). With four or more points, the probability is high for LQTS; with one point or less, the probability is low. A score of two or three points indicates intermediate probability.

- QTc (Defined as QT interval / square root of RR interval)

- ≥ 480 ms - 3 points

- 460-470 ms - 2 points

- 450 ms and male gender - 1 point

- "Torsades de pointes" ventricular tachycardia - 2 points

- T wave alternans - 1 point

- Notched T wave in at least 3 leads - 1 point

- Low heart rate for age (children) - 0.5 points

- Syncope (one cannot receive points both for syncope and "torsades de pointes")

- With stress - 2 points

- Without stress - 1 point

- Congenital deafness - 0.5 points

- Family history (the same family member cannot be counted for LQTS and sudden death)

- Other family members with definite LQTS - 1 point

- Sudden death in immediate family members (before age 30) - 0.5 points

The risk for untreated LQTS patients having events (syncopes or cardiac arrest) can be predicted from their genotype (LQT1-8), gender, and corrected QT interval.

- High risk (> 50%) - QTc > 500 ms, LQT1, LQT2, and LQT3 (males)

- Intermediate risk (30-50%) - QTc > 500 ms, LQT3 (females) or QTc < 500 ms, LQT2 (females) and LQT3

- Low risk (< 30%) - QTc < 500 ms, LQT1 and LQT2 (males)

A 1992 study reported that mortality for symptomatic, untreated patients was 20% within the first year and 50% within the first 10 years after the initial syncope.

Genetic testing for Brugada syndrome is clinically available and may help confirm a diagnosis, as well as differentiate between relatives who are at risk for the disease and those who are not. Some symptoms when pinpointing this disease include fainting, irregular heartbeats, and chaotic heartbeats. However, just detecting the irregular heartbeat may be a sign of another disease, so the doctor must detect another symptom as well.

Syndactyly and other deformities are typically observed and diagnosed at birth. Long QT syndrome sometimes presents itself as a complication due to surgery to correct syndactyly. Other times, children collapse spontaneously while playing. In all cases it is confirmed with ECG measurements. Sequencing of the CACNA1C gene further confirms the diagnosis.

Treatment for Romano–Ward syndrome can "deal with" the imbalance between the right and left sides of the sympathetic nervous system which may play a role in the cause of this syndrome. The imbalance can be temporarily abolished with a left stellate ganglion block, which shorten the QT interval. If this is successful, surgical ganglionectomy can be performed as a permanent treatment.Ventricular dysrhythmia may be managed by beta-adrenergic blockade (propranolol)

Currently, some individuals with short QT syndrome have had implantation of an implantable cardioverter-defibrillator (ICD) as a preventive action, although it has not been demonstrated that heart problems have occurred before deciding to implant an ICD.

A recent study has suggested the use of certain antiarrhythmic agents, particularly quinidine, may be of benefit in individuals with short QT syndrome due to their effects on prolonging the action potential and by their action on the I channels. Some trials are currently under way but do not show a longer QT statistically.

In some cases, the disease can be detected by observing characteristic patterns on an electrocardiogram. These patterns may be present all the time, they might be elicited by the administration of particular drugs (e.g., Class IA, such as ajmaline or procainamide, or class 1C, such as flecainide or pilsicainide, antiarrhythmic drugs that block sodium channels and cause appearance of ECG abnormalities), or they might resurface spontaneously due to as-yet unclarified triggers.

Brugada syndrome has three different ECG patterns:

- Type 1 has a coved type ST elevation with at least 2 mm (0.2 mV) J-point elevation and a gradually descending ST segment followed by a negative T-wave.

- Type 2 has a saddle-back pattern with a least 2 mm J-point elevation and at least 1 mm ST elevation with a positive or biphasic T-wave. Type 2 pattern can occasionally be seen in healthy subjects.

- Type 3 has either a coved (type 1 like) or a saddle-back (type 2 like) pattern, with less than 2 mm J-point elevation and less than 1 mm ST elevation. Type 3 pattern is not rare in healthy subjects.

The pattern seen on the ECG is persistent ST elevations in the electrocardiographic leads V-V with a right bundle branch block (RBBB) appearance, with or without the terminal S waves in the lateral leads that are associated with a typical RBBB. A prolongation of the PR interval (a conduction disturbance in the heart) is also frequently seen. The ECG can fluctuate over time, depending on the autonomic balance and the administration of antiarrhythmic drugs. Adrenergic stimulation decreases the ST segment elevation, while vagal stimulation worsens it. (There is a case report of a patient who died while shaving, presumed due to the vagal stimulation of the carotid sinus massage.)

The administration of class Ia, Ic, and III drugs increases the ST segment elevation, as does fever. Exercise decreases ST segment elevation in some people, but increases it in others (after exercise, when the body temperature has risen). The changes in heart rate induced by atrial pacing are accompanied by changes in the degree of ST segment elevation. When the heart rate decreases, the ST segment elevation increases, and when the heart rate increases, the ST segment elevation decreases. However, the contrary can also be observed.

A 2007 study followed 112 individuals for a mean of 12 years (mean age 25.3, range 12–71). No patient died during follow-up, but several required medical interventions. The mean final heights were 167 and 153 cm for men and women, respectively, which is approximately 2 standard deviations below normal.

NS can be confirmed genetically by the presence of any of the known mutations listed above. However, despite identification of fourteen causative genes, the absence of a known mutation will not exclude the diagnosis, as there are more, as-yet-undiscovered genes that cause NS. Thus, the diagnosis of NS is still based on clinical features. In other words, it is made when a physician feels that a patient has enough of the features to warrant the label. The principal values of making a genetic diagnosis are that it guides additional medical and developmental evaluations, it excludes other possible explanations for the features, and it allows more accurate recurrence risk estimates. With more genotype-phenotype correlation studies being performed, a positive genetic diagnosis will help the clinician to be aware of possible anomalies specific to that certain gene mutation. For example, there is an increase in hypertrophic cardiomyopathy in patients with a mutation of "KRAS" and an increased risk of juvenile myelomonocytic leukemia for a mutation of "PTPN11". In the future, studies may lead to a targeted management of NS symptoms that depends on what genetic mutation a patient has.

Radiologic diagnosis

Surgery is typically used to correct structural heart defects and syndactyly. Propanolol or beta-adrenergic blockers are often prescribed as well as insertion of a pacemaker to maintain proper heart rhythm. With the characterization of Timothy syndrome mutations indicating that they cause defects in calcium currents, it has been suggested that calcium channel blockers may be effective as a therapeutic agent.

JLNS patients with "KCNQ1" mutations are particularly prone to pathological lengthening of the QT interval, which predisposes them to episodes of "torsades de pointes" and sudden cardiac death. In this context, if the patient has had syncopal episodes or history of cardiac arrest, an implantable cardiac defibrillator should be used in addition to a beta blocker such as propranolol.

Andersen–Tawil syndrome, also called Andersen syndrome and Long QT syndrome 7, is a form of long QT syndrome. It is a rare genetic disorder, and is inherited in an autosomal dominant pattern and predisposes patients to cardiac arrhythmias. Jervell and Lange-Nielsen Syndrome is a similar disorder which is also associated with sensorineural hearing loss. It was first described by Ellen Damgaard Andersen.

Jervell and Lange-Nielsen syndrome (JLNS) is a type of long QT syndrome associated with severe, bilateral sensorineural hearing loss. Long QT syndrome causes the cardiac muscle to take longer than usual to recharge between beats. If untreated, the irregular heartbeats, called arrhythmias, can lead to fainting, seizures, or sudden death. It was first described by Anton Jervell and Fred Lange-Nielsen in 1957.

This condition is incredibly rare, with only 100 cases reported worldwide, however there are thought to be many cases that have been left undiagnosed. It is either inherited from at least one parent containing the mutated gene. or it can be gained through the mutation of the KCNJ2 gene.

In general, idic(15) occurs de novo but the parents must be karyotyped to make sure it is not inherited, mostly because this will affect the course of genetic counseling given to the family. If the abnormality is found prenatally and one of the parents harbour the marker, the child has a chance of not carrying the mutation. Further tests should however be done to prove the marker has not been rearranged while being inherited. This information is also necessary for counseling of future pregnancies. Each family is unique and should therefore be handled individually.

The extra chromosome in people with idic(15) can be easily detected through chromosome analysis (karyotyping). Additional tests are usually required. FISH (Fluorescent in situ hybridization) is used to confirm the diagnosis by distinguishing idic(15) from other supernumerary marker chromosomes. Array CGH can be used to determine the gene content and magnitude of copy number variation so that the clinical picture can be foreseen.

Interstitial duplications of chromosome 15 can be more difficult to detect on a routine chromosome analysis but are clearly identifiable using a 15q FISH study. Families should always discuss the results of chromosome and FISH studies with a genetic counselor or other genetics professionals to ensure accurate interpretation.

Kabuki syndrome can be diagnosed using whole exome or whole genome sequencing. Some patients who were initially clinically diagnosed with Kabuki syndrome were actually found to have Wiedemann-Steiner syndrome.

The ECG tracing in torsades demonstrates a "polymorphic ventricular tachycardia" with a characteristic illusion of a twisting of the QRS complex around the isoelectric baseline (peaks, which are at first pointing up, appear to be pointing down for subsequent "beats" when looking at ECG traces of the "heartbeat"). It is hemodynamically unstable and causes a sudden drop in arterial blood pressure, leading to dizziness and fainting. Depending on their cause, most individual episodes of torsades de pointes revert to normal sinus rhythm within a few seconds; however, episodes may also persist and possibly degenerate into ventricular fibrillation, leading to sudden death in the absence of prompt medical intervention. Torsades de pointes is associated with long QT syndrome, a condition whereby prolonged QT intervals are visible on an ECG. Long QT intervals predispose the patient to an , wherein the R-wave, representing ventricular depolarization, occurs during the relative refractory period at the end of repolarization (represented by the latter half of the T-wave). An R-on-T can initiate torsades. Sometimes, pathologic T-U waves may be seen in the ECG before the initiation of torsades.

A "short-coupled variant of torsade de pointes", which presents without long QT syndrome, was also described in 1994 as having the following characteristics:

- Drastic rotation of the heart's electrical axis

- Prolonged QT interval (LQTS) - may not be present in the short-coupled variant of torsade de pointes

- Preceded by long and short RR-intervals - not present in the short-coupled variant of torsade de pointes

- Triggered by a premature ventricular contraction (R-on-T PVC)

The treatments of kabuki syndrome are still being developed due to its genetic nature. The first step to treatment is diagnosis. After diagnosis, the treatment of medical conditions can often be treated by medical intervention. There are also options in psychotherapy for young children with this disorder, as well as the family of the child. Genetic counseling is available as a preventative treatment for kabuki syndrome because it can be inherited and expressed by only having one copy of the mutated gene.

Signs of Rett syndrome that are similar to autism:

Signs of Rett syndrome that are also present in cerebral palsy (regression of the type seen in Rett syndrome would be unusual in cerebral palsy; this confusion could rarely be made):

Myofibre break-up, abbreviated MFB, is associated with ventricular fibrillation leading to death. Histomorphologically, MFB is characterized by fractures of the cardiac myofibres perpendicular to their long axis, with squaring of the myofibre nuclei.

Treatment is directed towards the withdrawal of the offending agent, infusion of magnesium sulfate, antiarrhythmic drugs, and electrical therapy, such as a temporary pacemaker, as needed.

Because of the polymorphic nature of torsades de pointes, synchronized cardioversion may not be possible, and the patient may require an unsynchronized shock (or defibrillation).

Despite the grave initial presentation in some of the patients, most of the patients survive the initial acute event, with a very low rate of in-hospital mortality or complications. Once a patient has recovered from the acute stage of the syndrome, they can expect a favorable outcome and the long-term prognosis is excellent. Even when ventricular systolic function is heavily compromised at presentation, it typically improves within the first few days and normalises within the first few months. Although infrequent, recurrence of the syndrome has been reported and seems to be associated with the nature of the trigger.